Sensei, Kowai Hanashi shimasen ka

Reiji Hizuki is, by all accounts, a normal high school Japanese teacher, but he's thrust into the middle of a mystery when he moves to another town for a substitute teaching position. The woman he's replacing disappeared two weeks ago, and rumor has it that the problem child of her class, Kyouichi Magaki, was seen with a blood-stained knife the day before she vanished. The cops are on his trail, but what really happened to Sakuraba-sensei? And how are Hizuki and Magaki involved?

(Source: Taisetsu Project)