The Memorandum of Kyoko Okitegami

The Memorandum of Kyoko Okitegami (忘却探偵シリーズ, Okitegami Kyouko no Bibouroku) is a manga written by Nisio Isin and illustrated by Asami You.

Plot
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.

Kyouko wants Yakusuke to keep it secret. chapter 5-6 page 36

From this day forth, you shall be known as Okitegami Kyoko, and you shall live your life as a detective.