I guess I have read chap. 24 now, enough to cause blisters in my eyes, but I have to say that the entire chapter is the culmination of the bathroom scene in chapter 3.
As most of us Saezuru fans have deduced by now, Yashiro is suffering a panic attack at the end of the chapter right after he came and this is because it is the first time Yashiro has cummed from being "made love to", not just from the animalistic/unemotional sex he's used to, which is what he had only allowed Doumeki to do before this. He feels vulnerable for responding both physically and emotionally to being made love (very gently) by Doumeki, and this is directly related to the bathroom scene in chapter 3 where Doumki asks if Yashiro wants to "hold him" and Yashiro replies that no, because from Doumki it would be "gentle, normal sex", which is something that Yashiro had never experienced until now, but that we can infer he probably has subconsciously yearned for his entire life. He fears succumbing to Doumeki's tender love because he truly believes it will fail, that it is hopeless and that he would be emotionally destroyed by it and this is most likely rooted in his inferiority complex and self-repudiation he himself is unaware of. Yashiro subconsciously believes he's unworthy of love or that such pure sentiment is impossible for him.
Analying this bathroom scene, when Doumeki asks him if he wants to hold him, Yashiro does not immediately reply, there is a marked pause before he answers, as if this is the first time in a long time he's considered it, this was purposely done to allow us a peek into Yashiro's inner yearnings, to infer that he might like/want/be curious of/crave to have "gentle, normal sex" [which he probably did want in the past with Kageyama] but he shakes himself back to (his pessimistic) reality and replies to Doumeki in the negative. In short, Yashiro feels himself both unworthy and incapable of intimacy, of being loved and loving back; and even if he feels greatly tempted by Doumeki to consider it, he fears being destroyed by it too much to risk opening himself to the emotion. That bathroom scene may seem very simple and inconsequential, but I would argue it is one of the most powerful moments of the entire story because it told us a lot about Yashiro's fears:
http://www.mangago.zone/read-manga/saezuru_tori_wa_habatakanai/mf/v01/c003/33/
It's not that he hasn't experienced gentle, normal sex. I believe he has experienced it twice. First was from his stepdad - yes it was child rape but it wasn't rough, a bit of bondage but he was held gently because if he was roughly handled, he wouldn't associate gentleness to be nauseating. Another proof would be when he was disgusted as that yakuza guy who supervised him before held him "like a woman", from one of the posts at domeyashiro, it was discussed that Yashiro had the same expression from when he was raped as he did it with the yakuza guy. And he hated their sex, thus his sadistic streak emerged despite Yashiro admitting that guy was decent or okay.
Which is probably why he wants rough sex, where men look down on him through sex, emotionless sex, since he feels disgusted of himself. Contrary to him saying that he likes who he is earlier in the chapters. Also, he doesn't want to be held the way his stepdad did. The dominating-monopolizing-full-of-desire-and-affection kind of sex is what he does not want to experience ever. So chapter 24 was Yashiro re-living that past and going through that trauma again, though because he trusts and also likes Doumeki, Y is letting him continue but figured it was too much for him. The treatment/drug (Doumeki) is too strong for Yashiro.
Seriously, I imagine ch 24 like a therapy session for Yashiro.
Portuguese translation up to chapter 11 for Portuguese and Spanish speakers:
http://centraldemangas.org/mangas/info/cinderella-plot
Russian translation up to chapter 15:
http://yaoichan.me/manga/12279-cinderella-plot.html
I couldn't appreciate this manga; the art style is an erratic convoluted mess that made me dizzy as I tried to decipher what was going on; also, the plot consists of the lowest common cliche denominator using the rape trope very ineffectively as it was gratuitous and unsightly, with a weak and hysterical uke and a very unlikable seme.
You can find the entire raw first volume at Yaoiotaku:
http://www.yaoiotaku.com/forums/threads/37912-odoru-ecstasy-natsushita-fuyu-%5Bjp%5D
You just need to register, which is no big deal, download the .rar file and extract it with a free zip/rar opener like 7-zip
Oh fuck...the feels on this one are devastating. My heart is in pieces and I'm seriously bawling here ╥﹏╥ (/TДT)/ aggggg!!!