Kōhei has dark blond hair and a relatively lean and muscular medium build. He has been described by many characters as being very attractive, although his eccentric personality usually puts off admirers. He is usually seen wearing shirts sporting anime characters and when drinking with the diving club, he is usually naked or in his boxers.
Kōhei is a hardcore otaku and can sometimes be seen as a pedophile or pervert as he seems to be obsessed with most anime and manga archetypes, particularly little sister characters (hence his obsession with Shiori). While many are repulsed by his otaku lifestyle, Kōhei does not seem to care or mind what other people think about him. He is also easily manipulated when bribed with things such as meeting with seiyuus. When not struggling in class or indulging in his otaku obsessions, he can be seen drinking and partying wildly with Iori and the rest of the diving club members.
- Iori Kitahara: Kōhei's fellow classmate and club member. Their relationship begin with a rough start with him being swindled by Iori into joining Peek-a-Boo against his will. Despite this, he and Iori were able to get along just fine though they do sometime are at each others throat due to their eccentric and silly antics. They are best friends.