Bijuu is a member of the Family, or the Rotschstein Institute. He is mentioned by Kia in The Other Yandere. Apart from his association with the Family/Institute, as well as the Yandere Program, all that is known is that he, along with Dr. Rotschstein, favored Kara Gentner among the yanderes, finding her "particularly beautiful."

This character is very likely named after the YouTuber Bijuu Mike, who played several AppSir games on his channel and is a known fan of yandere games and other types of anime games.