Deciding his obesity needs to be addressed, Tamako, Choi and the others decide to put Dera on a mochi-free diet until he loses enough weight to fit into a birdhouse Kanna made. In order to keep watch over Dera to make sure no one feeds him, Choi goes to school with Tamako and the others, where she joins in on classes and helps Dera get some much needed exercise, before going to a used clothes store. As Dera shows up the next day with a curiously slim body, Kanna and Midori give Choi a sweater they made for her.