With students tasked with forming three-girl units for the upcoming Autumn Festival, Tsubasa invites Mahiru to join her unit alongside Yozora, which they decide to name Sky-Girl. Meanwhile, Yume, still downhearted following Koharu's departure, decides to skip on the festival to focus on training. After going through some rigorous training, Mahiru ends up joining the others for a pajama party designed to help bring them together as a unit. On the day of the festival, Mahiru works up until the last moment to create new dresses to unify their unit. As Sky-Girl manage to give a great performance, Yuzu and Ako approach Yume about joining their own unit for the Autumn Festival.