Oumagatoki is an horror first person perspective adventure game that takes place during the summer of 2001 when Tatsuhiro Oka Yuutarou, a young man is chasing a woman (called Kyoko), who was running in Tokyo in the evening. When he catch her a sudden flash of light appears, and they are transported into the Edo Period. He lost his memory, and the player starts to go around the village and during the game he will recover his lost memories. The player will have to solve the mystery.

The game is divided into 3 chapters and when the player complete them a fourth one can be played. A save at the end of this game can be used at the start of the sequel Oumagatoki 2.