While some of the girls venture into Vatler's floating ship, Akatsuki and Himeragi end up alone in the school gymnasium. They have no memory of the prior day and are bewildered as to why they are sharing a futon and why Himeragi is wearing a PE uniform with bloomers. The mystery deepens as a bloodstained baseball bat is found, along with a missing weapon, and a purple bra discovered in the MCs' pockets. As different groups attempt to uncover the truth behind the deserted boat, the bloody bat, and the purple bra, the stakes only get higher.