"Euphoria" follows Takato Keisuke and six others trapped in a mysterious futuristic complex, forced to participate in a sadistic game where Keisuke, as the "unlocker," must sexually violate one of the girls, the "keyhole," in specific acts to survive. Refusal to play results in brutal punishment or death, pushing the captives into a harrowing struggle between dark desires and the hope for freedom. As the twisted game unfolds, Keisuke battles his own disturbing urges while trying to protect those he cares about.