Lee Chan-ho

During fourth period, high schooler Da-jeong finds her classmate Tae-gyu dead in a classroom and Jeong-hun standing in front of him with blood on his clothes. In order to stop Jeong-hun from becoming the prime suspect, Da-jeong must help him find the real murderer, who is still inside the school building, under 40 minutes before period four ends.

A lazy gym teacher Seong Geun is completely content with his easy gig teaching high school P.E, but times are getting tough and his job is in danger. When Seong Geun's school decides to sack a gym teacher in favor of an English teacher, he too makes an important decision. To survive, he must teach English! Seong Geun whole heartedly makes the switch from PE to ET (English Teacher), but there's only one problem: he doesn't speak English.