曽我 尚樹

He has been in the same class as Souma for 5 years.

He's always hanging out with him as they get along well together.

He's a guy who gets dead serious about all things erotic. Says that it is all he has going on for him.

He's also a liar. But the vast majority of said lies are utter nonsense, which is also why Souma can stick around him.