Atsumari first appears alongside Ruka, telling her that her belongings have been placed in her locker at the doujinshi convention. She then asks Ruka what her objective is coming to Ikebukuro.
Later, backstage at Ruka's concert, she bursts into the dressing room, asking Ruka to hurry up and go to the stage for a final rehearsal of her show. She is surprised to find Hayate in there. She asks Ruka who he is, and Ruka responds by saying that he is her relative. Another man then calls Atsumari, asking her if Ruka is ready, and she replies affirmatively. While she sees Hayate helping out backstage, she mulls over whether Hayate really is Ruka's relative.