3-nen A-gumi: Ima kara Mina-san wa, Hitojichi Desu

Ibuki Hiiragi works as an art teacher. He began teaching at his current high school two years ago. He is the homeroom teacher of 3rd Grade A Class. 10 days before graduation day, Ibuki Hiiragi stands in front of his 29 students, including Sakura Kayano, and tells them "From now on, you are hostages."