At Cafe Seiren, Tsubasa reveals to Itsuki that she is to appear as the 15th Amrita Girl, who serves as the face of the Amrita Shower line of drinks. However, the director of the commercial she is set to appear in has stated that she lacks "devilish charm", and needs Itsuki's advice on how to address this. Touma, who had gotten off work early and came by to visit, explains that she needs to be more "suggestive", describing it as like a cat. This gives Tsubasa the idea to look for a stray cat named Little Devil for a better understanding.
Itsuki and Tsubasa find Little Devil in an alleyway, and Tsubasa begins observing the cat, attracting a crowd. Even Kiria notices, and comments on how Tsubasa will always give it her all, no matter the task. Eventually, Tsubasa comes to an understanding that she needs to show fans what they want without giving it to them, causing her Performa to awaken. After performing Radiant Unity, Caeda notes Tsubasa's unique way of thinking in certain situations. The commercial is aired successfully, but Tsubasa's interaction with Little Devil has been covered by a magazine, much to her embarressment. She then comments to Itsuki that she'll try to be more "devilish" from now on.
Completing this side story unlocks Tsubasa's Ad-lib Performance Tsubasa's Kiss, based on her appearance in the Amrita commercial.