Okitegami Kyouko no Bibouroku

The first instalment of the Boukyaku Tantei Series.
Okitegami Kyouko, also known as the forgetful detective. She forgets everything in a day, and solves cases (almost) immediately! An unfortunate young man, Kakushidate Yakusuke, gets caught up in every case and is always the prime suspect! He cries out, "Please let me call a detective—!!!"
A swift development, a fleeting memory.
Will Kyouko-san be able to solve the case before she forgets its details?
(Source: Kodansha, translated)