After a childhood friend's suicide, Hideaki and his former classmates reunite to pay their respects. Soon after, a DVD, marked X arrives revealing a man being tortured, triggering a flashback in Hideaki, reminding him of witnessing a schoolmate being subjected to humiliating batsu (punishment) games. One evening, Hideaki is kidnapped and when he awakens the next day, he discovers he is in a recreation of his old school-room, along with his fellow classmates. Trapped and held captive by mysterious hooded figures, each of them must now play a brutally violent, version of the punishment game, in order to survive.

Akari Yoshiyama is graduating high school soon and is expected to lead new life after she passes the university entrance exam, while her mother is working as a pharmacologist. However, her mother has a car accident and the situation is totally changed. She decides to go to 1972 to fulfill her mother's wish.

The year is 1947, during the war torn period of the Showa era. The story begins when a man, presumed to have been killed in battle, returns home. Who was this man? Before the war, he had a bright future ahead of him as the proficient and popular rakugoka (comedic story-teller), Usagi Morinoya. However, because of an injury sustained during the war, his face is covered in bandages, and he suffers from total amnesia. As if trying to recover his memory, the man only keeps mumbling in a hollow voice his trademark rakugo, "Sokotsunagaya".

High school student Kyosuke Shikijo is the most talented member of the school's martial arts of the fist club. His late father was detective and Kyosuke share his father's strong sense of justice. Kyosuke also has a secret. Kyosuke likes to wear female underwear and transforms himself into the alter ego "Hentai Kamen," wearing female underwear and gaining superhuman powers. This unusual interest also comes from his parents, with his father a masochist and his mother a sadist. By chance, Kyosuke gets the underwear of female high school student Aiko Himeno. With her underwear, he gains various pervert techniques and attempts to protect Aiko from a dirty and heinous teacher.