Chou Tantei Jikenbo: Rain Code - Oresama-chan wa Oyome-san!?

The amnesiac protagonist, Yuma, wakes up at a train station and discovers through his luggage that he is a detective working on a case. Yuma heads for "Kanai Ward," where he was supposed to investigate the case with the Shinigami who haunts him. However, an incident occurs on the train they are on...?