In a vibrant city in South Korea, the life of a young architect, Ji-hoon, takes an unexpected turn when his little sister, whom he has always protected, moves in with him after a family separation. The sweet and charming Soo-yeon quickly becomes the center of his world, filling his home with laughter and heartwarming moments. However, what begins as a harmonious cohabitation becomes complicated when Soo-yeon shows interest in a mysterious new boy in the neighborhood, an enigmatic artist named Min-seok, who seems to be more interested in her than Ji-hoon had expected.
As the relationship between the sister and her admirer develops, Ji-hoon finds himself increasingly trapped in a whirlwind of jealousy and concern. Struggling to balance his role as a protective brother with the need to let his sister make her own decisions, Ji-hoon is challenged by his own feelings for Soo-yeon.
With a light tone and moments of uproarious comedy, the film explores the boundaries of sibling love, youth, and the feelings that intertwine in relationships. Hilarious and emotional situations unfold as the characters navigate the confusion of love, loyalty, and unexpected self-discoveries. In the end, each must confront their fears and desires, discovering that sometimes, true love can mean letting go.