As summer break continues, the Seidoukan Academy prepares for their annual summer festival, which is a grand event that attracts visitors from all over the city. Ayato and his friends are busy helping out with the preparations, from decorating the school grounds to practicing their performances for the festival.

Meanwhile, Ayato receives a request from the student council president, Claudia, to investigate a strange occurrence that has been happening in the city. Several people have reported seeing a mysterious figure with unusual powers, and Claudia suspects that it may be related to the recent disappearance of several high-ranking executives from a powerful corporation. Ayato agrees to help and begins his investigation.

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As Ayato and his friends continue their preparations for the festival, they encounter a group of students from another academy who are also participating in the festival. Among them is a girl named Saki, who catches the attention of Ayato's friend, Eishiro. However, their friendly encounter takes a dark turn when Saki reveals that she is actually a member of a group of assassins hired to eliminate Ayato and his friends.

With the festival just around the corner and the threat of assassination looming over them, Ayato and his friends must come up with a plan to protect themselves while still enjoying the festivities. As the day of the festival arrives, tensions rise and the stage is set for a showdown between Ayato and the mysterious figure with unusual powers, as well as the group of assassins out to get them.