In a deviated timeline, Yui is sent back to July 13 instead. She joins the Astronomy Club during summer vacation in Nagisa's villa and enjoys hot spring with them. The following day, a storm hits while they enjoy the beach, leading them to take shelter in a war plant. As they explore the plant, the club members encounter a wandering ghost that put Sö in a sleep, and frightened Airi and Kaori. The ghost is found by Yui then she uses the black box to temporarily merge their timelines...