Synopsis

Yuha is a child who writes handwritten letters. Once a week, he writes a handwritten letter and sends it to his grandmother, who writes back. Yuha and her grandmother enjoy the fun of exchanging handwritten letters together. Yuha writes to her grandmother once a week. Every time, she goes with her mom on the same day of the week, but her mom tells her that she already mailed the letter last week, so she doesn't have to go today. She adds that she also mailed a letter to her friend. Suddenly, a warning siren sounds in Yuha's head. She rushes to her room and finds that the letter, or rather, the secret diary, is indeed missing. Her mother had thought it was for Davin, so she put a stamp on it and sent it off.

It wasn't actually a letter, it was just written on letter paper. I wrote it on letter paper like a letter because that's what I wanted to say to her. But I had no intention of mailing it. It was just a diary entry filled with stories about how I hated her for taking the strawberry cake. "If you keep doing that, I won't be friends with you, so be careful!" she wrote. She poured out her heart in the letter.

Yuha and her mom have already tried everything to find the letter. They go to the post office, and also check the mailbox at Davin's house. But Yuha can't bring herself to open it. Will Yuha ever find the letter that is growing bigger and bigger in her heart? Can he get it back before Davin gets it?