In the sleepy, coastal town of Bellview, the summer heat is relentless, and the days blend together. , a 19-year-old guitarist with a rare form of synesthesia (where he sees sounds as colors and lights), feels trapped. He dropped out of music school because the noise of the city was blindingly bright. He came to Bellview for silence, but he found only boredom.
Upon entering the shop, Eun-gyeol is transported back to , where he meets his father, Ha Yi-chan (Choi Hyun-wook), at eighteen. To his shock, he discovers that his father could hear and speak at that age—and was even leading a band to impress a girl who was not Eun-gyeol’s mother. Eun-gyeol joins forces with his teenage father to form a band called Watermelon Sugar , hoping to change his parents' difficult fate while unraveling the secrets of their youth. Core Themes and Impact