Onodera Kyouya

The ability - of immortality. The drawback is that it experiences gradual memory loss, resulting in a maximum memory retention of two years. Gender - Male. Age - 17 years.

Kei has dirty blue hair and azure eyes. He wears a dark blue school uniform, but keeps his collar and tie loose.

After the timeskip, his appearance remains the same, possibly due to his inability to age. He now wears a dark blue security guard uniform with a lightning bolt on the top.

The potential number of murders by Kyo is unknown. Kyoya calls others "omae-san," which translates to "my dear" (manga translation) or "kid" (anime subtitles). This is an outdated term (お前さん, omae-san) that is rarely used by Japanese people today. His sense of smell doesn't work, so he uses sticky notes to know when the expiration date of things like food has passed or if they've gone bad. He entrusted his notebooks to Foucou, and she was the only person who knew about his lack of talent for a while.

The deuteragonist of the series. He transfers to the school on the same day as Nana Hiiragi. He comes across as unfriendly and rude. He is a cautious person who doesn't easily reveal his abilities. His observational and reasoning skills are on par with Nana's, and he is also an avid reader and very well-informed.

Koya is a lone wolf, showing no interest in what's going on around him. At first glance, he gives the impression of being dark and dangerous, to the point that Moko says he probably killed someone in the past. However, as the story unfolds, we see Koya's true personality: he's a somewhat socially awkward person who sincerely wants to make friends but has no idea how to do it. He's very straightforward in his desire to make friends, as he directly asks Nana and Fuuko how to make friends and befriend him.

His most remarkable quality is his intelligence and deductive reasoning. Koya is a logical, rational, and observant person, as shown from the very beginning when he discovers that two of his classmates are in a relationship (this is based on one having the left side wet and the other the right, meaning they shared an umbrella). Furthermore, he several times anticipates some of Nana's plans, demonstrating a great analytical ability on his part. Thanks to his intelligence and ability to deduce things, he suspects Nana's actions and suspects that she is behind the disappearances and death.

He knows little about more commonly used slang (he asks Nana what "swag" and "F-boy" mean) and seems more like an old-fashioned person. He usually speaks strangely (using the outdated お前さん (omae-san), which translates to "dear" or "child") and has a taste for retro video games.

It was also shown that he has diverse hobbies. His room contains many different books on various subjects, indicating that he is a well-rounded person with a broad range of knowledge. He is likely an otaku, supported by his love of manga, idols, and pop music, plus when he called two of his classmates "gyarus."