It’s Summer, which means Summer Vacation, which means swimsuits. Amane wants to attract a man, and asks Tao to use her crystal ball to help her pick one out for that purpose. For her part, Nanako doesn’t even own one, as she hasn’t been in a pool since she was little.
Amane takes Tao, Nanako and Kino to the store where they are faced with far too large a selection. All the while, Tao’s ball suggests a slingshot bikini for Amane that is “just strings,” while Eiji is ambushed in his room by Koto in a stunning black bikini. If he’s going to have eyes for another girl, she’s clearly making sure he knows what he’s missing.
Nanako, by nature a modest person, starts out with a swimsuit indistinguishable from a dress, then a sarong, but eventually settles on a white bikini that catches the attention of everyone at the pool. It happens to be the same pool where Eiji is taking his little sister, which means he’s present for Nanako’s “grand unveiling” (Amane’s term, not mine!)
She runs back into the changing room, and when Amane tells him what the deal is, he apologizes to Nanako and tells her he’ll keep his distance and avert his gaze. Of course, Nanako wants neither of those things, and so rushes back outside to grab him and assert that it’s okay for him to look, a little—all using a tanzaku she seemingly conjured out of nowhere!