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.

Satoshi apologizes to Shion (still pretending to be Mion), and asks her to care for Satoko during the Watanagashi Festival. That night, his aunt is murdered; in order to cover for Satoshi, Shion reveals that she is actually Mion's twin sister. After the police questions her, she is brought back to the Sonozaki main estate to answer to her grandmother for all the trouble she has caused.

Shion believes the Sonozaki family is connected to the acts of "demoning away" people in the village, especially that of Satoshi. She imprisons Mion in the dungeon and unintentionally kills her grandmother. Shion pretends to be Mion the next day and confronts Keiichi about the previous night's encounters, to which Keiichi still denies. Later, she finally discovers the ones responsible for Satoshi's disappearance.

Rena discover the true character of her father's girlfriend and grows a deep hatred for her.