Battle Against a Demon Lord

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The entire city buzzed with anticipation as the day arrived. The entire kingdom had turned into a ghost town as practically every Harpy gathered to observe the event. As Naya led them, they could see the thousands of Harpies watching.

Since he was used to it, he was using his usual Kijin form, but this time he had simply swapped to the wings of a Harpy.

A barrier had been built with the magic that the Harpies knew, but since they didn't expect it to hold up with the fight, the main defense the Harpies took was distance, using their enhanced eyesight to watch from a distance.

"Woah, this looks serious." Milim exclaimed, her eyes wide with excitement as she surveyed the scene. "This is perfect for my grand reveal."

"Will it really make that much of an impact? You've kind of been laying low this whole time." Souka asked, causing Milim to freeze mid-air.

"Huh… I didn't really think this through, did I?" Milim asked, the joy leaving her voice.

"Don't worry. I'm sure Frey will at least be surprised, so you just have to record her face to keep it as a keepsake for later." Rimuru said, trying to prevent Milim from causing a mess before the fight.

Milim brightened up at that. 

"Good idea! I'll do just that."

As they reached the peak, the excitement in the air was palpable. The arena was the entire sky above the peak, and Frey was standing at the very top, her majestic wings spread out to showcase their full glory. It was both an act of intimidation and showmanship.

"Naya told me about your new form, but I must admit that I find it quite charming. The wings are usually the most attractive part of a Harpy. And yours are truly something to behold." Unlike the first time they had met, Frey had a soft smile on her face briefly, quickly replaced by her usual seriousness.

"In that case, I must tell you, your wings are unlike any I have seen before." Rimuru said, giving her a smile and a bow, causing her to chuckle slightly.

"That is not quite how it should be said, but I will accept the compliment either way."

Frey lifted into the air, amplifying her voice to address the crowd. 

"Are you ready, Rimuru Tempest?" She called out, her voice carrying over the excited murmurs of the crowd.

With a smile, Rimuru nodded, changing into his combat form and drawing surprised looks from both Frey and the crowd. However, Frey knew better than to let this shake her focus.

"Ready as I'll ever be. Let's begin."

The crowd fell silent, their collective anticipation palpable. Frey's wings flared out, catching the light and casting a magnificent shadow across the arena. She moved first, practically breaking the sound barrier with her speed becoming a blur of motion, her claws aimed directly at Rimuru's chest.

[Warning. Frey's speed is higher than your current speed in the air. Solution: Use Control Particles to solidify the air below your feet and allow the activation of Shunpo.]

[Warning. This action must be done before the effect of Magic Interference takes place.]

Following Sage's advice, Rimuru solidified the air beneath his feet and vanished, reappearing above Frey with his finger pointed like a gun. He fired a bolt of Dark Thunder. 

To his surprise, Frey managed to flap her wings with enough speed to dodge the lightning, which struck the mountain below, causing it to explode and reduce the size of the peak.

With another powerful flap of her wings, Frey whipped around, her eyes glowing with the activation of her skill, Celestial Eye.

"Impressive! I did not think you could dodge that. But can you handle this?" She raised her hand, summoning a whirlwind of razor-sharp Wind Blades that spiraled toward him.

The Wind Blades were strategically placed so that no matter where he dodged, one would be in his way. Rimuru, however, activated Gluttony, consuming all of them.

Frey's eyes widened in surprise, but she didn't hesitate. She flapped her wings and shot towards him, her claws ready to strike. Her Celestial Eye caught a glimpse of almost invisible strings blocking the path, but she deftly maneuvered around them with a flap of her wings.

"Are you ready?" Rimuru asked with a smile as he made his sword appear in his hand, the scabbard still on it as he swung to attack the speeding Frey. The clash of claws and steel echoed through the air, creating a shockwave that reverberated through the arena. Rimuru's scabbard met Frey's claws with a force that sent sparks flying.

Frey twisted mid-air, using her momentum to flip over Rimuru and attack from above. Rimuru, anticipating her move, solidified the air beneath him with Control Particles and propelled himself backward using Shunpo, evading her strike just in time before her Magic Interference skill came into effect.

"Is that all you've got?" Rimuru taunted, his eyes gleaming with determination.

"Hardly. I was just warming up." Frey retorted, her wings flaring out as she instantly vanished, her speed becoming even greater than before as she fully released her aura.

She was a Demon Lord Seed in terms of strength, and her entire fighting style focused on speed and decisive strikes. Had he come here just a few weeks earlier, she might have been able to mop the floor with him at her speed, but thanks to his fight with Gazel, he had improved his movement technique to the point where it could compete with her.

[Adjusting Strength… Calibrating due to the Magic Interference skill lowering effectiveness. Calibration complete.]

[Error. Magicule Interference has occurred. Control Particles cannot properly create a surface.]

[Analyzing Frey's Fighting Style…]

With his usual path of escape gone, Rimuru activated Thought Acceleration. He saw Frey, with a slight smile on her face, moving towards him at an impressive speed. Even with his increased perception of time, he had to complement her mentally because he could still see her body moving slightly as the rest of the world froze.

Instantly, he brought his wings in front of him to act as a shield. This caused Frey to think she had won. Because, in her mind, the moment she could attack him with her claws, she would be able to disable most of his Skills temporarily. Long enough for her to secure the win.

If she was being honest, she was slightly disappointed that the fight would end so quickly. She had hoped he would be the Child of the Storm, but if he couldn't win, it meant she wasn't the one for whom it was written.

As her claws were about to pierce the wings, they opened up like a donut, letting her hand pass through before suddenly compressing and capturing her hands. The sudden movement had caught her off guard, causing her to slam against his wings.

The moment she tried to move to dodge again, she felt a large amount of magicules gathering in front of her. Her wings instinctively moved to dodge, but her hands were being firmly held in place, long enough for the Dark Thunder to strike.

The thunderous roar of the Skill resonated across the entire battlefield, causing Frey to freefall for a few seconds before she snapped out of her shock and flew again. But that pause had been long enough for Rimuru to jump in her direction.

Before she could dodge, she felt a fist strike her, followed by claws slashing at her. She frowned in pain before flapping her wings and vanishing away, making some distance to regain her wits. As she did, she felt the air around her heat up before the black Hellfire enveloped her.

If it wasn't for Magic Interference making the magicules around her go wild, she would have been burnt to ashes. She gritted her teeth as she shot out of the ball of flames, her wings scorched slightly as she tried to claw at him again.

Rimuru anticipated her attack, shifting his position mid-air to counter her. He swung his sword, meeting her claws with a force that sent shockwaves through the arena. Their clash was fierce and relentless, each trying to outmaneuver the other.

Frey's eyes narrowed as she realized Rimuru was adapting to her every move. She needed to change tactics. With a powerful flap of her wings, she created a massive gust of wind, forcing Rimuru back. She then instantly began to fly, moving so fast it looked as if she was teleporting in a random pattern.

Her movements were unpredictable, or, well, they should have been.

[Analysis complete. The location of the next move has been found.]

Rearing his sword back, Rimuru swung it perfectly to strike the location where Frey appeared, surprising her as she got struck and sent spiraling through the air before she was able to control herself again.

Frey's magicules began to bubble up as she let out a shout of determination before her wings flapped again, appearing instantly in front of Rimuru and stopping him from using Shunpo with her Intrinsic Skill. However, she wasn't able to take the opening she had created.

"Damn it!" She shouted, instantly flapping her wings again, moving as she saw countless threads wrap around the place she had just been.

She didn't have a moment of rest as she had to dodge and move out of the way of the Dark Thunder and Hellfire, but with each attack, she took more and more damage.

Rimuru, for his part, wasn't idle. He kept up the pressure by chasing Frey down, and even though he couldn't quite reach her due to her speed, she could not fight back. Her strength was speed, and with Shunpo, he could almost match her.

If his Particle Breath worked through her Magic Interference, he would have been able to finish the fight by paralyzing her, but all it did when he last used it was create a smoke screen.

[Analysis complete. Transferring information on how to best maneuver using your wings.]

In an instant, Rimuru's speed increased until he crashed next to Frey, grabbing her with his talons as she did the same. They grappled in mid-air, each trying to gain the upper hand. 

"Let's finish this!" She said with a smile as she tried to stab her hand into his chest, but since he was a slime, he was able to open a hole for her hand to pass through without touching him.

Grabbing her hand to stop her from moving, he felt her grab onto him too, smiling.

[Warning.]

"Dodge this!" She shouted with a wide smile.

Activating her Unique Skill: Reflector, she shot back all of the damage she had taken throughout the fight, the fire, the lightning, the punches, and the slashes. All at point-blank range. 

An explosion resonated throughout the battlefield. However, sadly for her, Rimuru was immune to fire, resistant to lightning, and his body had been wrapped in the Armorsaurus armor the moment she shouted.

Though the armor shattered upon impact, Rimuru was still mostly fine. With a flap of his wings, he grabbed her even tighter before flying both of them towards the ground and crashing, sending an explosion of dust into the air.

A moment after the crash, Frey activated Reflector again, sending another explosion. But by this point, she had taken too much damage.

Breathing heavily, Frey looked at Rimuru, a mixture of frustration and admiration in her eyes. 

"You truly are remarkable, Rimuru."

Rimuru, standing over her, reached down to help her sit up. Noticing her injuries, he retrieved one of the countless Full Potions from his stomach and handed it to her. As she drank, she couldn't help but marvel at how quickly her wounds healed. She had tried countless High Potions before, but none compared to this one.

With a graceful flutter of her wings, Frey rose into the air and landed softly on the ground. She nodded at Rimuru, a faint smile playing on her lips. 

"Perhaps I underestimated you slightly. You have proven yourself worthy, not just to me, but to my people. But there's one thing you should know."

Frey then took a deep breath, her expression turning serious.

"Now that you have completed the Skybound Trial and bested me, you and I are one. It is a marriage tradition. The entire reason the Skybound Trial was created was for outsiders to challenge the Queen for their hand in marriage, and since you've won..."

"Oh really?" Rimuru asked with a chuckle, already having guessed where this was heading.

"Yes," Frey continued, her voice steady but with a hint of mischief. "It's tradition. You have proven your strength and worth. As the leader of Fulbrosia, it is my duty to ensure our lineage remains strong. Of course, if you are opposed to it, I will not force you. However, in the eyes of my country, we are already one."

"What?!" A sudden shout pierced through the air as Milim shot out from her spot, appearing in front of them. "You tricked him! That's not fair!"

Milim's sudden defensiveness surprised Frey. 

"Milim? Why are you-"

"Rimuru is my best friend, so I can't have other people take advantage of him! Not even you, Frey!" Milim declared with a slight frown before she felt Rimuru's hand land gently on her head.

"It's fine. I had already guessed what it was about."

Milim looked up at him, her eyes wide with surprise. 

"You did?"

"Yes, it's not like they were being very subtle about it. Plus, your priestess, Naya, kind of made it obvious when she asked me to change forms into a Harpy."

With these words, Naya moved from the crowd and landed with the group, bowing her head to them.

"The Hero who saved the first queen left a message with us countless years ago. I am glad that I have witnessed the fulfillment of their message during my life."

"A message from the Hero?" Rimuru asked, his interest piqued. He had read about them in the history books in Fulbrosia, but he didn't have much information about them otherwise. 

"Yes, the first Hero who saved the Queen left us this message. It has been passed down from generation to generation, and now, it is my time to deliver it." Naya said with an almost fanatical smile as she took off the bandages on her face, revealing her white eyes. 

"In the twilight of destiny, the winds shall whisper tales of the future. Hear now the words etched in the fabric of fate:

The Child of the Storm, ruler of the forest, shall arrive. United, you shall soar above the clouds, vanquishing the enemies of our kind. In the union of hearts, the bond of Storm and Harpy shall be forged.

From this sacred union, the Harpies shall ascend to unseen heights, guided by your leadership. Through the harmony of Storm and Harpy, the true queen shall emerge, destined to be the mightiest of all Harpies.

Embrace this destiny, for it is through your alliance that the Harpies shall find unparalleled success, surviving the war where all things end. "

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Special Thanks to my Beta Readers/Editors: The one, the only, the amazing @Basilisk, the Aussie @LuluViBritania (FF.N, SB, WN and QQ)/-LuluViB|99th Britannian Emperor(Discord) and @Kiyan Tribe (FF.net/AO3/QQ/WN) | kiyan_tribe( Discord)

Go Check out Basilisk's great story "I'm a Daemon, so what?"