Taking Itsuki someplace private, Kiria requests that he find Sir Gen, a plushie that she keeps, which she dropped while she was at Daitama. When he finds it, however, it is in tatters due to being stepped on. Per Tsubasa's suggestion, Itsuki takes it to Ayaha to have it fixed.
Rather than fix it herself, however, Ayaha instead opts to teach Itsuki how to sew in order to fix it himself. When he presents the repaired plush to Kiria, she admits to being worried about it, and decides to put her energy into her new song, causing her Performa to awaken. After performing a Radiant Unity, Tharja teases Kiria about Sir Gen, claiming she's even more attached to him now that Itsuki's fixed him. Later, after performing her new song The Labyrinth, she talks to Itsuki about the feelings expressed in the song. When he brings up the plush, however, Kiria claims it is simply a memento.
Completing this side story unlocks Kiria's Ad-lib Performance The Labyrinth, based on the song of the same name.