A voyeur is regularly sneaking a look at the girls' bath, and the students are tasked with catching the culprit. Meanwhile, Jail attempts to find out more about this timeline and figure out why Nana sent them here.

Rihito decides to receive the operation to turn him into an Ace. This is the decisive moment in history that the time travelers wanted to change, but knowing what they know now, they cannot agree on what is best for everyone.