Riko Tsukimi is the homeroom teacher for Tooru and Julie in Kouryou Academy. She has just graduated as a student from Kouryou then became a teacher. She knows all of Sakuya's secrets and is also an acquaintance of her. Since Tooru has a duo of the opposite gender, most of her perverted jokes are directed towards him, which causes misunderstandings around him. (Source: Absolute Duo Wikia)