Yumeko, the daughter of a doctor in a certain town, is a tomboyish and strong-willed girl who finds a tall young man lying in the forest covered in blood and shirtless for some reason. His name is Sanosuke. However, he says he doesn't remember anything other than his name.
Not wanting to abandon him, she takes him under her wing for a while, but even after time passes, his memory doesn't return... He has no particular behavioral problems, and after his wounds heal, he begins working as a carpenter in the town.

Yumeko suggests that they exchange letters, including practicing, with Sanosuke, who cannot read or write. Before she knows it, she is attracted to Sanosuke, who is trying his best to live his life despite having lost his memory.
She invites Sanosuke to the fireworks festival and they stay alone at the inn. The two of them quickly become closer, but it seems that this is not the first time she has seen him move around without his memory. Where did he come from, and how did he end up in that forest? Who is he...?