A CODA (child of deaf adult) student born with a gift for music crash lands at an unfamiliar place after time traveling through a suspicious music shop. There, he forms the band Watermelon Sugar with other mysterious youths.

People are busy watching the screen. The person wearing a mysterious mask so called 'Gaetal' appears, and the Killing Vote begins.

The series is about an incident that takes place when the owners of the boarding house called 'Guest Summer Palace', which breaks stereotypes, and boarders with secrets gather to find Lee Seol who disappeared 13 years ago.