He's been Rokuro's best friend since childhood. When Rokuro first arrived at Hiinatsuki Dorm, he was the one who looked after him and helped him settle in—basically got him to actually smile again. They've stayed close ever since.
He eventually moved out of the dorm to pursue work as an exorcist, which meant he wasn't around when the Hiinatsuki Dorm tragedy went down.
Content compiled by AnimeList.moe from publicly available sources.
