Natsume Mochizuki is a teenager whose life in Tokyo as a fashion model comes to an abrupt end when her family relocates to the remote countryside town of Ukigumo. Struggling to adjust to the slow pace and isolation of rural life, she feels trapped and disconnected from her former identity. Everything changes when she meets Koichiro Kō Hasegawa, the enigmatic heir to a wealthy and respected local family who is known for his rebellious and unpredictable nature. Drawn to each other with an intensity that borders on obsession, their relationship awakens deep and tumultuous emotions that neither of them fully understands.

As Natsume and Kō navigate the fragile and often destructive boundaries of their bond, the story follows their evolution from middle school through adolescence. The narrative explores how their connection strains under the weight of outside pressures, including the attention of classmates and the expectations of their families. A significant turning point occurs when the couple faces a traumatic event that threatens to tear them apart, forcing Natsume to confront her own vulnerabilities while Kō struggles with feelings of failure and inadequacy. This leads to a painful separation, during which Kō moves away to pursue a career in entertainment, leaving Natsume to grapple with her feelings and rebuild her sense of self.

Years later, as young adults, Natsume and Kō are brought together once more for a funeral, forcing them to confront the unresolved feelings of their past. Their reunion challenges them to decide if the love that once consumed them can evolve into something more stable and mature, or if the wounds of their youth are too deep to heal. The film is set against the contrast of bustling Tokyo and the serene, almost mystical coastal landscapes of the fictional Ukigumo, a setting that mirrors the emotional turbulence and isolation of the main characters. Key supporting figures include Katsutoshi Otomo, a kind-hearted local boy who offers Natsume a gentle alternative to Kō's intensity, and Kana Matsunaga, whose presence adds further complexity to the group's social dynamics.