Twenty-five-year-old Kakushidate Yakusuke suffers from the fate of constantly stumbling into various crime scenes and ending up being the main suspect.

His last resort: Okitegami Kyouko the "Quickest Detective." However, Kyouko suffers from a strange case of amnesia; whenever she falls asleep, she forgets everything that happened the previous day, making her solve the mysteries within one day.