It’s summer time! Kyuhyun, a high schoo student, spends his holiday in his uncle’s house. His uncle, who named Leetuk, has a toy shop there named Doll Castle. Because Kyuhyun doesn’t want to bother his uncle for staying there, he helps him on the toy shop as the shop keeper. In Kyu’s life, he has never fallen in love with someone whereas he’s 18 already. And this summer... His first customer is his first love?