Jilted and heartbroken, 20-year-old Kinoshita Kazuya turns to Diamond, a Rent-A-Girlfriend app that leads him to a fateful encounter with Mizuhara Chizuru, one of the talents on offer.

Immediately after deciding not to rely on pretend dating anymore, Kazuya is hit with a triple whammy of reveals: Chizuru not only goes to his college but lives next door to him, and his grandmother is coming to visit and wants to see her.

Kazuya barely has time to deal with the fallout of the situation in the pub before the gang heads off on a short trip to Izu, where they run into someone unexpected.