Mahou ni Kakatta Shingakki

It is spring, and Kotomi has just transferred to a new high school for her third year. At the opening ceremony, Kotomi discovers that the boy she knew as "Maa-kun" during childhood is actually the Japanese history teacher! After school that day, a first-year student is involved in an incident that seems to have occult origins, which causes Kotomi, Maa-kun, and three other students to be sent to a different space. What happens there...!?

(Source: Hakusensha, translated)