The hentai is based on the visual novel of the same name by Studio Mirisu.

The Taisho era. It took place between the Meiji and Showa eras. Deep autumn - yellow and red leaves covered the mountains and plains. The protagonist arrived in a small provincial town and brought with him something that could help with the autumn festival. Having fulfilled his duty, he decided to take a walk along the familiar streets of the town. Nostalgia consumed him, and he didn't notice how he came out to the embankment where he met her. It was love at first sight, mad love...