Interlude: Rias

Mitsunaga Seigi was a mysterious person to say the least.

He was tall, with black hair and eyes, and good looking as well. Despite the fact that he didn't participate in any sports, he was extremely fit for his age. He had all the makings of a popular kid but was a recluse who spent all his time to himself.

But apart from that, he was just like any other regular human. Rias never felt any type of energy or aura from him that showed that he had connection with the supernatural. He had never made contact with Sona or Rias, nor did he ever deviate from his normal behavior.

Rias could have written off Mitsunaga Seigi, but she didn't, because Rias knew there was something wrong about him. Maybe other devils might have been fooled by his normality, but Rias was the sister of the current Lucifer. She knew firsthand that appearances could be deceiving, just like how she knew that her doting older brother was one of the strongest beings alive.

That was how Mitsunaga Seigi felt to Rias. He felt like her brother, in the way they both radiated power without even trying. Despite him not being any special, Rias's senses told her that if she pissed him off, then she would die. That was how she gained an interest in the elusive 'Quiet Prince' of the academy.

She had sent her peerage to slowly befriend him, which did not work at all. She had thought that Kiba would be the one to succeed because of him being male and having the same popularity. Even Akeno, because of her identity and womanly charm. They both failed, with Mitsunaga only engaging in polite discussion or just avoiding them all together. The fact that he could avoid them in the first place already confirmed her guesses on Mitsunaga.

Surprisingly, the only one who succeeded was Koneko, and that was because she wasn't really trying. Even then, it was more a relationship of acquaintances then actual friends. Koneko basically reported nothing except for what food he brought that day, and Rias had learnt nothing except for the fact that Mitsunaga was a really good cook.

Thus, she had no choice but to ask for help from Sona. Although she grumbled a bit about helping, she agreed to accept him into the Student Council to keep an eye on him. It did help that Sona had suspicions of her own which she told Rias.

Mitsunaga Seigi was her biggest suspect on the true identity of the "Slayer".

The "Slayer" was an embarrassing topic for the both of them. Considering that they were the ones who ran the territory, it was humiliating that a random person was doing their job better than them.

The presence of the Slayer was first discovered after Rias and Sona found that several Strays that were reported to have wandered into their territory were gone. There was no body that remained, and not even Koneko could track down where the perpetrator went. That should have been the end of the case, but the 'Slayer' continued to act.

The Slayer seemed to have upped their game after they discovered his trail, with his Stray body count going higher and higher. In fact, the mysterious vigilante even started to show up in towns outside of Kuoh, killing with extreme prejudice. This gathered him a large amount of acclaim in the supernatural community.

Many theories were made about the Slayer's identity, such as an excommunicated priest on a vengeance path, a magician who wanted new bodies to experiment with or Stray devil who devoured other Stray devils. Rumors like that exploded, since it had been a while since such a thing had occurred and that it mainly happened in the territory of the two Satan sisters.

In the end, the responsibility to find out the Slayer's identity landed on them. Thus, they began sifting through the list of suspects to see who it could be. Most of the work was done by Sona though, since investigation was more a part of her specialty than Rias. Her and her peerage mostly acted as grunts for Sona's evidence gathering.

They were easily able to get information on most of the suspects through hypnotism and confirmed that they weren't related to the incidents. It was only after deciding to interrogate the students did, they find their most likely suspect.

Well, he was the most likely suspect because there was no way to confirm his involvement or not. Hypnotism, it seemed, did not work on Mitsunaga Seigi, which was weird in and of itself. Among ordinary humans, only those who have great willpower could break through a devil's hypnotism. Those are the people who had struggled through many obstacles in life or have lived through harsh circumstances.

Mitsunaga Seigi was a teenager who had suffered no such hardship, with the only thing setting him apart being his parent's divorce. Even then, they had split amicably, and still kept in contact with each other. His father worked abroad, but he also regularly sent letters and gifts to his son back home.

So that must mean Seigi was resisting using supernatural powers, just ones that Rias couldn't see. Which made him the most suspicious out of all the people on the list. After all, he was the only person that wasn't cleared.

Now that they had narrowed it down to Mitsunaga, Rias had set up surveillance all over his house. This method seemed to have failed, as nothing wrong ever showed up when Mitsunaga was shown. He was perfectly within the parameters of a normal human. It was Sona who had used it to confirm that Mitsunaga was more than he appeared.

The directions in which he came from, and the distance put him in a position where he could have killed the Stray Devils. Not to mention that had snuck glances at the camera, which showed that he knew they were there. Though why he did not just avoid them was still a mystery to Rias.

Sona wanted them to hold off on confronting him until they her peerage could ingratiate with him, which Rias admitted reluctantly, they were doing much better than they did. That way, they didn't drive him into a confrontation the moment they brought it up. After all, they didn't know how much he knew about the factions, and they didn't want to fight with someone who could kill that many devils and walk away unscathed and untraced.

Rias also agreed, as she didn't want to scare away a future member of her peerage. She knew that Sona was also interested in him, but Rias saw him first. Rias was certain that Mitsunaga would make a great knight.

As for what to do if he rejected her? She didn't think that something like that would happen. After all, who would reject an increased lifespan, greater magic, and the support of the house which spawned the current Lucifer?

They would have to be a madman.