(Reiji, pls this be the case. I trust in you) Either Kazuya gets shittalked a lot by the gang of fuckboys, Umi attempts to make a move on Chizuru, but she turns Umi down, Kazuya witnesses, gets a confidence boost even though he still doesn't know Chizuru heard his previous half-confession. Kaz, somewhat slightly affected by the alcohol, admits he failed to protect her, but Chizuru confesses she heard everything the other time. Kazuya, feeling cornered, admits he was being sincere, despite of the interruption. As a consequence, they grow closer... but their convo was cut short by Ruka who was waiting for him at the apartment, visibly pissed. She only manages to slap the shit out of him, Future Kazuya monologues about "having deep feelings for someone come with a high cost, and that he learned, by unconsciously hurting Ruka at that moment he needs to be clear about his feelings not only to Chizuru, but to everyone" . Chapter ends with a shot of Kaz's broken phone with" You have 50 LINE messages and 10 missed calls" notifications. Next arc is about Kazuya, helped by Chizuru, Mini and Kuribayashi of all people, trying to amend things with Ruka, because he feels things shouldn't end in a bitter way, as he can't really blame her for falling for him, now that he realized thanks to Kuri and Chizuru he has something that makes girls fall for him, and not a superficial quality, but a really deep one...
OR (ffs, pls this drama scenario doesn't happen, pls)
Kazuya gets shittalked a fkn lot by the fuckboys at the party, Nanao (Umi's ex, which he dumped because he wants the Chiz so badly) is also there bc of reasons, Umi makes a move on Chizuru and forces a kiss on him, Kazuya witnesses from afar, dead shineless eyes to signal his mind and heart were broken. He takes a taxi back to home, and Nanao is with him, because it happens she lives near Kaz and Chiz, equally broken. A small talk about the shocking moment naturally happens, Nanao politely thanks Kazuya for accompanying her to her home, casually talking about streets being dangerous for a woman. Broken Kazuya sees a figure waiting for him at the apart... it's Ruka, with a serious face. She nags him because he didn't replied the 50 msgs and one call, but notices something on his dead eyes.
Kazuya casually, and with a funeral voice says something about her being right about him not having to involve with a rental girlfriend because he was just a client. Ruka laserguides his thoughts and goes "aaaahhh kawaisou ne Kazuya, it must have been hard on you. That girl was only leading you on, she always was out of your league", Kazuya starts to spontaneously and seriously cry and blaming himself for being such an idiot. Ruka, being the clingy and touchy feely girl she is, embraces him and tells him everything is gonna be alright, he's not a bad guy at all... and forgives him (subtle signal she sees herself above him in a relationship). She reminds him about october 31st.
Meanwhile at the party, Chizuru is visibly pissed bc Umi kissed her, slight flashback of the fray, with Umi being bitchslapped, called out by Chiz, and being told how dare he to do such a thing, they are just friends, yadda yadda and that she likes "you-know-who". She tries to find Kazuya at the party, but can't find him. She figures he saw Umi kissing her and stormed off the party. She has a really, really bad feeling and now she fears Kazuya might build his own emotional wall between them due to a misunderstanding, despite of the huge effort he made to make that wall crumble, now a misunderstanding might drift them apart and she doesn't want that. Next 20-30 chapters are a role reverse and now she is the one who chases him, but she has it harder because the trial run turned into an official relationship, only because Kazuya jumped to conclusions and is broken beyond repair.