Takao, who is training to become a shoemaker, skipped school and is sketching shoes in a Japanese-style garden. He meets a mysterious woman, Yukino, who is older than him. Then, without arranging the times, the two start to see each other again and again, but only on rainy days. They deepen their relationship and open up to each other. But the end of the rainy season soon approaches.
One day, Naho Takamiya receives a letter written to herself from ten years in the future. As Naho reads on, the letter recites the exact events of the day, including the transfer of a new student into her class named Kakeru Naruse. The Naho from ten years later repeatedly states that she has many regrets, and she wants to fix these by making sure the Naho from the past can make the right decisions—especially regarding Kakeru. What's more shocking is that she discovers that ten years later, Kakeru will no longer be with them. Future Naho asks her to watch over him closely.
A fourth-grader investigates the mysterious reason behind the sudden appearance of penguins in his village, which is somehow related to a power from a young woman working at a dental clinic.
