The great detective has met his match! Middle-aged detective Eiji Kirisame has finally given in to the strange high-schooler Tsugumi's marriage proposal, and now they've started living together! As her new fiancé, Eiji's saddled with the responsibility of having to join Tsugumi in a visit to her parents' house... but surely nothing could go all that wrong in just one night, could it? To make matters worse, Eiji may finally have found a truly unsolvable case...