Maou no KyoushitsuLa clase del Rey Demonio; Maou no Kyoushitsu; The Demon's Classroom; 魔王の教室; 魔王的教室

An oneshot by Yoshikawa Miki; a teacher for the fifth graders claims to be the king of the underworld!? Some of the students then decides to investigate him, is he really from hell?