Prologue

3rd month of winter, year 290th After War Era:

In the highest mountain located in the Dragon King Verdor's mountain range, a silhouette of 2 people were seen checking on a magic circle that shined faintly, having a large crystal located in the center of it. Surrounding the magic circle are several metal-like contraptions, each of them carved with a lot of runes which seems to sucking the nearby mana, judging from the faint whirling of wind around it before being funneled towards the large crystal. It seems like they're conducting some sort of ritual in this inhospitable area.

"Hmmm, the magic circle is perfect, the mana amplifiers works fine, the aetherite crystal seems to accumulate mana exactly as we calculated. I really hope this will work out fine. How about you Gwen-sensei, can you detect any abnormalities?" I said to the girl besides me.

"Hmmm nope, it works as fine as we intended. And we've done teleportation magic multiple times already so don't be such a worrywart my idiotic disciple." replied the girl, known as Gwen-sensei to her disciple.

"I know sensei, but all of our experiments only involve people or items across this world. What we are doing right now got a higher hurdle you know? We are going to teleport people between worlds after all, so excuse me for becoming a little bit skeptical."

"What, getting cold feet already? Have some faith in me, have I ever misled you before? Plus this is your idea in the first place, so just be grateful that I'm willing to help you, stupid disciple." quipped her.

"Yes, you're right. This was my idea after all, thanks for the help sensei. Vee, how long do we have to wait until the aetherite crystal finish charging?"

[It'll be done in T-minus 10 minutes Takeru-sama. Should I remind you when it's done, master?] replied a synthetic-like voice, coming from the pendant that I wore around my neck.

"Do it, Vee."

[Affirmative]

The mountainside become silent once again as we observe the ritual. The calm atmosphere accompanied by the faint lighting from the magic circle was cut short by a sudden question from sensei.

"Come to think about it stupid disciple, it has been 300 years since the first time we met with each other haven't it?"

"…ah yeah, it has been that long huh? It felt like just yesterday when you found me in the forest, dying from being attacked by goblins and decided to take me as a disciple since you found me as 'an interesting specimen'."

" Fufu~ It's not common to feel that kind of large space time anomaly around here so I decided to investigate. Look and behold, I found a teenager wearing some kind of weird getup getting beaten up by goblins at the location. Kinda hard for me not to laugh seeing someone dying for an enemy that even kids can beat." laughed sensei.

"Hey, it's not my fault okay?! I was just trying to find out where the hell I was and they ambushed me all of the sudden. Plus don't compare me the people of your world, they're monsters I tell ya!" I countered her. The physical strength of this world's people is several times higher compared to my old world, probably due to plenty of mana available.

"Hmmm not gonna lie you're weak as fuck in the early days, now you're somewhat decent I guess. All of it was due to my genius mind though. Nah, can't hope for all people become as talented as me." Sensei dissed me while not forgetting to praise herself at the same time.

"Yeah yeah, my sensei is the world's best. We peasants can only grovel under her feet. And I don't know what will counts as 'great' if becoming the strongest man in the world can only counts as 'decent'." I grumbled ending our banter.

But 300 years huh? Time sure do flies, I thought as my mind wanders through my memories. My experience in this world, Valvria all started when I was suddenly transported here via a portal appeared below my feet when I was going home after I had some fun at a game arcade nearby. By the time my consciousness returns, I, Shin Takeru, a normal 17 years old highschool student found myself in a forest out of nowhere.

The first thoughts that come out from my otaku mind were 'Is this the fabled isekai? But where's the god that'll give me a cheat? Or where is the beautiful princess that will give me the whole SOP rundown? Or where is my standard isekai beginner package? All I have is what currently on my body though.' It took me awhile before I start to accept my new reality and decided to get out of the forest in order to at least find some sort of civilization somewhere.

This didn't last long however as I was suddenly attacked by what I assumed goblins since they look the same as the ones from the games I've played. I tried to defend myself but failed spectacularly due to several reasons. First, they appeared out of nowhere. Second, I don't know shit about fighting apart from punching and kicking randomly, plus I ain't an athletic person, I'm a bona fide otaku. The third and last reason was there's like, 5 of them ganging up on me so I'm bound to fail.

And failed I was, going to die bleeding from various injuries thus cutting my isekai adventure short before a beautiful elf come to save my ass, marking my first meeting with the Elf Sage Gwendlyn, my sensei. Finding me as 'an interesting specimen', she decided to take me as her disciple where I was taught magic theories by her.

After I somehow got the theories dialed on, she then appointed me as her assistant in her various projects, which irked her since I'm fine with magic knowledge but my mana level aren't reaching the satisfactory level she intended. This situation lead to her conducting some experiments on me in order to improve on my mana capacity which sometimes nearly killed me. But the experiments was successful and I finally got my cheat, a body with high mana capacity that allow me to use high ranked magics to blow up things to kingdom come for days and nigh infinite lifespan with perpetual youth. However, my face was still stuck with average Japanese looks, but hey, silver linings.

My joy was cut short by sensei, saying that I still can't worth a damn if I didn't have enough stamina and techniques to fight properly. Which makes her to proceed to threw my ass towards her old friend, Guildmaster Lyle Vermont or better known as Master Lyle for some martial arts training. He was apparently the former history's strongest Knight Captain in Brittania Empire, the place I'm currently at. He's a tough old man that gave me a hell of a training which lasts for about a year before he deems me as a passable warrior in his books. Damn training nearly ended my life multiple times, again and I also need to help him in some guild odd jobs every time he called for the training fee.

From there on, my lifestyle went back to become Gwen-sensei's assistant and being Master Lyle's gopher in-between for a few years. During that duration, I did ask sensei if she got some ways for me to return back to my home world but her answer wasn't as positive as I hoped. Teleportation magic does exist, but requires astronomical amount of resources for it to work reliably, plus they can only cover for a short distance, about 100 km at most. Techniques for a long range teleportation across continents had lost due to the ancient civilization's destruction by the demons. So unless I somehow manage to magically learn the ancient teleportation techniques outta nowhere and have fuck ton of money to spend on the project I can kiss my dream to go back home to see my parents in a short period of time goodbye.

I felt sad a little bit, but hey life must go on, am I right? So I just decided to keep on living here, who knows if I can do it in the future. Plus the life's here ain't that bad, I'm currently living a peaceful lifestyle with a hot busty brunette elf teacher, maybe I can woo her so that I can make my lifestyle more vibrant? That plan went down the drain quickly when I found out later on that she's more into yuri, so press 'F' to pay respect. Oof. But she still makes a great conversation partner for cultural discussions though.

The peaceful days where cut short however when the fire nation attacked, I mean when the demons began attacking all of the races living in this world. They suddenly woke up from their slumber one day, managing to break through the ancient civilization's barrier surrounding the inhospitable demon continent and starting their attack on nearby countries, closing rapidly towards Brittania Empire thus jumpstarting the 'Humanity vs Demons' arc.

The Empire, being the strongest nation in the world, began rallying nearby countries for an alliance and calling all able bodies throughout the empire to join their cause. Gwen-sensei and and Master Lyle were summoned to the capital in order to join the elite taskforce formed from various strongest people across the world that'll be spearheading the alliance army towards the demon continent, ending the invasion once and for all. I was of course included in the elite taskforce since I was their student, and apparently that was a big deal for the Empire royalties since they hardly took disciples if ever.

It was there where I met the first and last of my love, the princess of Brittania Empire, Princess Kallen vi Brittania. She joined the elite taskforce as the main healer since she was hella good at it, plus being the High Priestess of Freya Church pretty much sealed the deal since they're all about purging the unholy being after all. At first I was confused when the first time I saw her, thinking why the fuck she looks exactly the same as Kallen Kaslana, one of the main protagonists in Kallen Fantasy game series that I played frequently while in highschool? Even her name was the same, apart from her family name of course.

But then I get rid of that kind of mentality since this is real life after all and we got a more important matter like hordes of demons to purge. She's a good girl though, always focusing the good in people instead of the bad ones and we've managed to become good friends, dunno what she saw in me. During the early days of the expedition, I didn't dare to confess to her since she was a beauty and a royalty to boot, not like me who's got average looks and was a commoner nobody.

And from there on our journey with the alliance army which took years begin, killing a horde of demons at a time before moving to next one, while slowly closing on the demon continent. The demon hordes were weird as hell I tell ya, not much that we know about them apart from a few excerpts and tomes discovered from the destroyed ancient civilization's ruins. From what we've learned, the demons horde emerged every time their queen wakes up from her slumber and starts mass producing her minions before they have enough numbers and energies to break through the ancient barrier encirclement surrounding the demons continent. Why did them hell-bent in destroying any living being nearby was anybody's guesses.

The demons mostly resembled the monsters we normally seen in this world apart from colored in white with pink lines all across their bodies, plus turning into some pink-like cubes and vanish when died, leaving no carcasses behind. Plus they emit some kind of energy that corrupts any living beings, turning them into their zombie minions if they didn't have enough mana to counteract the corrupted energy. That caused many soldiers with low mana capacity to die and turning into zombies when exposed to the corrupted energy for far too long, thus increases our losses. It took us a lot of time to devise an effective method for us to combat the demons properly. This newfound method increases the alliance army's morale as we marched closer towards the demon continent.

It was during this journey also I managed to make my relationship closer with Kallen, thus making us becoming lovers. I guess sharing sweat and tears while enduring challenges together makes a good recipe for love relationships to bloom, who knew. And Gwen-sensei adding some love rom-com moments by cockblocking me every time we're about to do some intimate things, getting jealous since Kallen chooses me instead of her. Master Lyle was just watching us from the sidelines though, enjoying it like some kind of drama performance while drinking his wine.

Kallen and I also did make a promise to get married and then rebuild the destroyed empire together and all that sappy shit after we managed to bring an end to the demon invasion. Too bad our happiness didn't last long since she died during the final fight with the demon queen; she and Master Lyle got blasted by the demon queen's stray energy beam into smithereens, leaving nothing behind. This makes me rages uncontrollably, thus jumpstarting my fight to the death with the demon queen while Gwen-sensei provides support and protecting the alliance army that were fighting the demon hordes nearby from our battle.

In the end of my battle with me managing to defeat her, the entire landscape for miles radius away became even more inhospitable than before, with the demon queen's minions starting to disappear and the alliance army managed to retreat safely to the temporary camp nearby. Gwen-sensei had to pick up my dying and out of mana ass from the battle location though.

This mark the end of 'Humanity vs Demons' arc, we along with the alliance army tended our injuries and begin pack up to go back towards our respective nations bringing the good news and the losses incurred during this whole expedition. The Brittania Empire royalty decided to make a new calendar dubbed the 'After War Era' to commemorate the end of war with the demons and rewarding me with the title of 'Valvria's Savior Hero'. This caused my fame to soar throughout the Empire and the world respectively for my deed of slaying the demon queen.

I however didn't have any mood for any kind of celebration since I've just lost Kallen, the love of my life and Master Lyle, my master/friend at the same time. Took me awhile to recover from the depression and move on into fulfilling my promise with Kallen, which was rebuilding the destroyed empire. I, along with Gwen-sensei who decided to join me on her whim began the empire's reconstruction.

With Gwen-sensei's expertise in various fields especially magic and the ideas from my home world, we managed to revive the empire way passing its golden age, with technologies reaching the Industrial Revolution Era in my home world. That's without the whole pollution thingy of course, we got the eco-friendly mana after all. All of these experiments and testing for the modern techs took a lot of time though, part of it due to my lack of knowledge on how these things works since I was just an average highschooler and sensei needing time to translate my ideas via trial and error, but we've managed to wing it somehow with enough time spent.

My hectic lifestyle went on for about a hundred years until I was satisfied in turning the empire into something that Kallen would be proud of. Gwen-sensei and I who were already bored living in the Empire decided to begin our next journey, which was travelling around the world to find some ancient civilization ruins, perhaps we can learn some useful lost knowledge from them. It was during that time I've decided since I had enough wealth collected during the past century to might as well starting the project that I've shelved long time ago, which was making a working teleportation magic ritual for crossing worlds.

My idea was approved by Gwen-sensei and therefore we started our journey around the world, looking out for the ruins while working on the teleportation ritual as a side project as we gleamed the knowledge obtained from the said ruins. Our journey covered a large area with us moving across various locations, from multiple nations and tribes, sometimes entering deep into dangerous areas none dare to venture into. It did nets us some good results though. By the 150th year of our journey, we had collected enough information for us to work on a feasible world-crossing teleportation ritual. Now it only needs some trial and error testing before I can feel confident on using it.

During this journey also was the time when we managed to make an AI named Vee, a shortform of Artificial Intelligence Version V, the fifth iteration of the series. I made her due to my random conversation with sensei on one night about the technology marvels in my world since we got freaking robots and advanced computers after all. We've made her in a form of a pendant but she can also switch into maid automata mode stuffed with tons of firepower since battle robo meido is cool so I thought why not.

After that we decided that we've enough of travelling and returned back to the Brittania Empire to find a place to stay and then start having a slow life while doing projects in between. It was during our journey back home that as if were fate dictates we found a destroyed village with only one survivor, an approximately 7 years old little elf girl who was heavily injured. The village was overrun by a random monster horde, leaving only herself who luckily survived. So we treated her and then bring her with us along the way, planning on dropping her on orphanage in the nearest town and then moved on.

The plan didn't worked however because first, she lost all of her memories perhaps due to the injuries and trauma; and second, she got hella attached to me since my face was the first thing she saw after waking up. Is this the famous parent imprinting? I dunno, but she won't stop gripping my clothes tightly while crying loudly when we tried to leave her at the orphanage. The situation becomes a little bit awkward for me, with judging glares of Gwen-sensei, Vee, the orphanage matron and the people from the surrounding area. So caving under their combined stares, I've decided to adopt her. Uuuh, taking care of children can't be that hard right? Named her Elaina, dunno whether it's a good name or not, Gwen-sensei and Vee didn't complain so it can't be bad.

So back to the main point, we returned to Brittania Empire and found a great place on the countryside to start our slow life arc along with Elaina, our new companion. Got us into another awkward situation though, since the residents in the village assumed that Elaina was the child made between me and Gwen-sensei, which denied vehemently by her saying that I was just her manservant and Elaina was her long lost descendant. People believed the lie though, since Elaina looked nothing like me, she's a cute little ball of sunshine compared to the ole average look me.

Plus by this point of time, most people nowadays didn't associate me as the 'Hero' that saved the world after all, most due to people alive during that era already dead except the long living race like elves and dragons which mosts are introverts, rarely leaving their dwelling. My portrait drawings and statues' aesthetics left behind were enhanced excessively and bears no resemblance with my real face, therefore turning me back into a nobody. Not did I care though, damn ungrateful bastards. I wonder why did I spent all those years helping the Empire for these people? Oh yeah, my promise with Kallen.

Let's get back to Elaina shall we? Ah yes, my sweet little daugtheru. Not gonna lie I wasn't as interested in raising her initially, but over the years she managed to enter my heart slowly with her cheerful personality after she started to with open up herself more towards our group. She's also eager to learn new things and turned up as a genius after being tested by sensei, her brain absorbed knowledge like a sponge. On top of that, she showed a great talent in martial arts based on my observation during our training sessions.

When she'd reached her coming of age, we've decided to send her to the Brittania Empire's most prestigious academy for further studies with heavy heart, but hey sooner or later our little bird gotta stretch her wings. There she'd managed to finish the curriculum in record time and become the academy's most popular student, endeared by the whole students and teacher's body alike. Greatest talent in the century they said, and coupled with her blooming blonde beauty there were a lot of suitors aiming for her which successfully thwarted by yours truly.

I may or may not have stalked her from the shadows, and thus contributed to the academy's urban legends mentioning 'a black knight with dreadful aura will come reaping for life on whoever had ill intentions on our academy's elf fairy'. Well, she managed to graduate perfectly though, being offered a job as the academy teacher on the spot where over the years she raised through the ranks and becoming the youngest headmaster in the history on her 25th birthday, thus making us proud of her.

Satisfied with my daughter becoming successful in life, I've decided to focus back on the world transfer teleportation ritual that went into the back burner due to me focusing on my daughter's wellbeing. The trial and error took us about 15 years though, and here we are today on the mountainside conducting the true and final ritual. My long ass unimportant reminiscence got interrupted by Vee's announcement.

[Master, the aetherite crystal had fully charged at 100% capacity. Please step on top of the magic circle to begin the transportation ritual. Ritual will be initiated in 10 seconds, starting countdown, 10…9…8…]

"Well that was fast, better get going. I guess this is the end of our adventure Gwen-sensei. Thank you again sensei for your guidance and help throughout all these years, I dunno what'll happen to me without you. Please look after Elaina for me, just in case if I failed to find a way to return back here. Kill anybody who dared to woo or hurt her on my behalf." I entered the magic circle, then turn my body facing sensei and utter those sentences. My body starts to turn into particles as the ritual beginning to activate.

[7…6…5...4…]

"Yeah, you're a real piece of troublesome student but I'm a magnanimous person so I'm fine with it. And if you're that worried about Elaina, why did you do this ritual in the first place? Well whatever, don't worry about Elaina, I'll take care of her…as my wife that's it." sensei assured me, but not forgetting to say some questionable things while smiling smugly.

[3…2…1…Blast off!]

"Thank-…Wait what? Whaddaya mean sensei?! SENS-" that was all I've manage to say before I vanished, leaving sensei and the empty magic circle behind.

"Hah, gottem."

And there he goes, the person known in the Brittania Empire annals as the Valvria's Saviour, Hero Shin Takeru, departing from this world to return back to his homeland, where his new adventure awaits whether he aware of it or not. Will he manage to create a new legend? Only god knows.