That's Right. I'm His Little Sister.

After getting flustered by Kenji's demands to hide his bag from Shio and Ataru, Funabori ends up preempting the boys by sticking her own head in the bag. Kenji's little sister comes to visit her brother's club room, but ends up getting increasingly scared by the girls inside, then flees after Takao accidentally smacks her against a bookshelf. Takao tries to make nice with her to get closer to Kenji, but her attempts backfire.