Yasuyuki "Senpai" Yamase

About

He works with Ueda and is his senior, called "senpai" by both Ueda and Aki. Yamase is endlessly weirded out by Ueda, initially turning a blind eye to his "friendship" with Aki. However, he easily befriends Aki as time goes on, becoming one of his few friends outside of the yakuza. He doesn't know the true nature of Ueda and Aki's relationship, believing both of them to be straight.