Dong Bin runs a small surf shop by the sea, where Xiao Fang works. Haunted by guilt over a past accident, Xiao Fang drifts through his days without purpose. His routine shifts when Yuan Yong and Yang Fan arrive, looking not to surf but to take photographs. What begins as irritation turns into friendship, and the three grow closer over a series of encounters, culminating in a charged night of karaoke. As each struggles with uncertainty—escaping expectations, searching for direction, or simply enduring—Sonata of Wave traces a quiet portrait of youth suspended between past and future.