Keiichi meets Mion's twin sister, Shion; the two are so identical that Keiichi can hardly tell the difference between them. It is also revealed that Mion has a crush on him.

The events from Watanagashi-hen are retold from another point of view. Shion takes Mion's place in Hinamizawa and is lovestruck by Satoko's older brother, Satoshi, at their first meeting together. But after discovering about the trouble he spends to protect Satoko, Shion starts to loathe her.

Upon talking with Ōishi, Shion finds out Satoshi has gone missing and decides to investigate further into the mysterious murders over the past four years. One day at the library, Shion meets Takano, who tells her more on the history of Hinamizawa and its dark past. As the story skips one year to the present day, similarities between Keiichi and Satoshi brings back memories of Satoshi to Shion.