For all his more kinky potential love interests at school, Keiki’s home life is defined by a healthily affectionate relationship with his imouto, with whom he spends the most time this week. Okay, maybe they’re a bit too close, as her reaction upon him walking in on her is almost too calm, and she seeks advice from him about the color of her underwear, and they have no problem with close physical proximity.
A quiet day at home is punctuated from a visit by Sayuki, who apologizes for jumping him at the clean-up session, but deems it the result of him showing his “pet” inadequate affection. So she has him do dog stuff to her: shaking hands, patting her head…and rubbing her belly. It’s the last thing that Mizuha walks in on.
Immediately after an “emergency family meeting” where he smooths things over, Yuika arrives, also bored, and dresses Kaiki up as a bunny girl before again removing her underwear for him. Mizuha walks in on the middle of that, necessitating another meeting.
Basically, after Keiki dealt with Ayano and Koharu, Sayuki and Yuika reassert themselves as his two primary love interests. Finally, Mao calls him, aware that the other two were planning to visit him, and asks a very cryptic question about what he’d think about her being his girlfriend.
Later, Keiki is shocked to discover Cinderella’s white underwear has vanished from under his bed. He concludes either Sayuki or Yuika took them, which makes them the two prime Cinderella suspects. I for one am not so sure about that, or his further deliberations with Ootori and Shouma.
For one thing, Mizuha could have removed the underwear. For another, either Sayuki or Yuika could have taken them and not be Cinderella. Finally, Mao’s phone call is super-suspicious. Still, Keiki is hell-bent on discovering the culprit once and for all, so he isolates Sayuki and takes her out to a theme park in order to continue his investigation.