Yuzu doesn’t understand why she has such a crush on Mei, just that she does, but she knows the only way to move forward is to make those feelings known. To do that, she needs to be on better terms with her, and the universe provides. When the chairman collapses in his office, the first person to find him and call an ambulance isn’t Mei, it’s Yuzu.
Mei is grateful, and lets Yuzu call her by her first name (even if she doesn’t reciprocate), and Gramps even reverses his decision to expel Yuzu. His health scare has made him re-evaluate a lot of things he’d taken hard lines on, be it the new granddaughter he never asked for in Yuzu, or the decision to make Mei live with him.
Mei then returns to Yuzu and her mom’s house, but it couldn’t come at a worse time, considering Yuzu’s feelings for her aren’t very sisterly. Yuzu seeks clarity in a yuri manga (which Harumin sees and jokingly pretends to reinact the action within its pages), while Yuzu’s mom makes things worse by buying a double bed for the sisters.
Obviously, living with one’s (presumably unrequited) crush is not easy, and I can’t help but feel for Yuzu here.
That’s not the end of her torment, as when bedtime comes and she finds herself unable to sleep, she tries to steal a touch of Mei’s hair or skin, and Mei gets out of bed and unrolls a futon, claiming it’s too hot with both of them under the covers.
When Yuzu brings up Mei kissing her, Mei coldly dismisses it as merely a tactic to shut her up, demonstrating its effectiveness by coming in oh-so-close only to withhold a kiss. She states she has “no interest” in Yuzu, or in getting closer, hence her unwillingness to call her by her first name. Yuzu goes to sleep in the bed alone, angry, and in tears.
Adding insult to injury, since Mei is the rule-obsessed class president, Yuzu is unable to hang out with Harumi after school without both of them getting punished by having to clean the bathroom. When that’s done, Yuzu finds a note from Mei calling her to the chairman’s office.
Yuzu is excited by the note, but when she arrives, Mei has her yuri manga, and warns her to dispose of it lest rumors crop up. Yuzu snaps, pushes Mei onto the desk, kisses her, then breaks into tears.
If Mei is uncomfortable here, but the fact is she kissed Yuzu first, and that’s how Yuzu’s crush on her developed; they wouldn’t be on that desk without Mei’s earlier antics. Yuzu knows she can’t go back now that what’s done has been done, but gets off Mei, apologizes for being such a bad sister, and runs off.
Her running off, and Mei lingering in the office, doesn’t go unnoticed by Mei’s friend, right-hand woman, and enforcer Himeko, who immediately suspects something is very amiss. Just as Yuzu and Mei are trying to sort things out, Himeko will no doubt insinuate herself into the situation.