After working for six years in the advertising department of a large corporation, Seori boldly resigns and returns to her hometown. Once back home, she does nothing but sleep— until her younger sibling Bori nags her into joining a local sports center to build up some stamina. That’s how she ends up signing up for swimming lessons. There, she encounters Yujeong, the swimming instructor. However, She doesn’t recognize him as Bori’s friend. Only Yujeong realizes that it's Seori, his first love—and his heart races. Beneath the blazing sun, in the cool waters of the pool, and through the humidity of the rainy season— a summer-flavored romance, full of heart-fluttering moments.