Ritsu and Fumiya met at an old coffee shop and eventually fell in love. However, a misunderstanding arises between Ritsu and Fumiya. After a fight, Ritsu leaves the house and is involved in an accident, losing only the memory of Fumiya.

A popular teen and a cheerful classmate fall into a secret romance, facing insecurities and learning to meet each other halfway.

The drama tells the story of a group of seven university students who travel to a deserted island where a strange decagonal mansion stands. It was the scene of a grisly mass murder six months earlier, and events soon turn ominous.