Nothing could tear them apart when two spirits find one another. Widower Takumi (Shido Nakamura) lives a quiet life with his six-year-old son Yuji (Akashi Takei) following the loss of wife and mother Mio (Yuko Takeuchi). Yuji unfailingly remembers her promise to him"I'll be with you again in one year's time, even once the rains come." Whenever they come across a woman sheltering from a monsoon downpour on the first anniversary of her passing, Takumi and Yuji are taking a walk into the woods. She's an uncanny resemblance to Mio, but has no recollection of who she is or exactly what she does there. Family life resumes from where they left off, while Takumi and Mio's memories in their first encounter at high school come flooding back. However, their new lifestyle is interrupted by the discovery of Mio's old diary, which reveals that the secrets of her past and how they must say goodbye once more in six weeks' period...