Bimii is a flying cat who has always accompanied Eruna from the moment she was accepted in the Academy. Although he did properly introduce himself to Eruna, Eruna didn’t manage to hear his real name so she decided to nickname him Bimii instead, from his bimyou (lit. questionable) appearance.
He is also the teaching staff of Mikagura Academy, as many of the students recognize and call him as Sensei. However, unlike Kurumi he’s never seen teaching students and it seems his duty is to follow a single unique student in each year or act as the referee during battles. He also seems to know the particular traits of each student quite well and get along well with them.
Details are currently unknown but he apparently transforms into a human