Hibiki Kanau

Kanau is a ghost haunting Mitsuo's high school. He had a tragic death, in which he and his senpai had agreed on committing a double suicide by jumping off a bridge. However, at the last moment, his senpai could not bring himself to do this, and turned away, but by this time Kanau had already jumped. Kanau is very jealous of Hasunuma's intense love for Mitsuo; the sort of love he was denied in his lifetime. Kanau manages to push Mitsuo out of an upstairs window, but is shocked and guilty when Hasunuma, fearing for Mitsuo, jumps out as well. Eventually, Kanau becomes somewhat of a pet for Mikuni. Source: Wikipedia