The Jo brothers, Jo Gyu-bin (uke) and Jo Eun-bin (seme), grew up in a family that was the envy of others. Despite this, their relationship was so strained they hadn't had a proper conversation in over ten years. A sudden accident, however, leaves Eun-bin with amnesia, regressing him to the mental age of an elementary schooler. Blaming himself for the incident, Gyu-bin takes responsibility and begins to care for his brother.

Struggling to cope with his adult-bodied brother who acts like a young child—throwing tantrums, sitting down in the middle of the street, and clinging to him while crying—Gyu-bin is startled when Eun-bin secretly visits his room late one night.

"Hyung, my pee-pee hurts," Eun-bin whimpers, unaware of what an erection is or how to relieve the urge through masturbation.

Flustered and partly out of anger, Gyu-bin ends up having sexual relations with him. He immediately realizes his mistake but initially dismisses it, thinking, I'll just play with him until his memory comes back. Even if it does, he'll be too embarrassed to tell anyone. This mindset, however, quickly pulls him into a mire from which he can no longer escape.