Nana visits Subaru's home and sees that he gives Haru too much food. To gradually decrease the intake, she gives him a bottle that dispenses food by rolling so that Haru can eat and exercise at the same time. Nana leaves forgetting to take her home key with her, and Haru is too attached to it that she would not let go. Subaru takes Haru to Nana's apartment and he meets her two cats Roku and Hachi. Haru becomes highly attached to Hachi...