Defeat Orihara-sensei's Supllementary Exam: Let's Rediscover Ton-chan-sensei's Past

Ikki, Kazu and Onigiri are having trouble with schoolresults on school, they planned on stealing the answers of the exam. In the progress they hear the story from Tomita Mari, the homeroom teacher of Ikki, about the school clock that's been frozen at one minute before half nine.