On the first Sunday of November, the three members of Tsubomi (ブゥトン) gather, and Yoshino (よしの) makes a shocking announcement. She declares that she will choose her little sister through an audition! With the deadline for selecting a little sister set by Eriko-sama approaching, Yoshino, who has had no luck in meeting anyone, comes up with this plan. Yumi (ゆみ) feels a sense of discomfort, but Sachiko-sama (さちこ) seems strangely enthusiastic and tries to get Yumi to participate. The next day, the newspaper club is also aware of the audition, and troubled Yumi consults Shimako (しまこ), but...!?