Just read the raws and I'mma help you out a little with that synopsis;
Misono keeps going into heat 'cause in omegaverse usually when a fated pair meets one another they can't control themselves till they bond (the omega gets bit on the neck). Any time he is near Hirose his heat follows 'cause of this.
He goes into heat despite taking more than the recommended dosage for suppressants and this is what triggers the swim team leader to lose control of himself (which is what happens in omegaverse lol) but before anything can actually happen either Misono dumps the TL into the pool or he falls in himself. Later on the TL apologizes for losing his cool and actually helps them out a bit.
The new alpha (from what I can gather runs with a really bad crowd) either recognizes or notices Misono and that he's an omega. I'm guessing he uses this as a pretense and tries to blackmail Misono into doing things with the other alphas. Unable to fully follow through with it despite being blackmailed he remembers Hirose and runs away.
This is where it gets weird 'cause now I think that yakuza alpha is on Misono and Hirose's side seeing as he tries to set them up in a hotel room alone together and then acts surprised over something Hirose tells him (I'm guessing it's something to do with them not bonding yet) but now there's a skeezy teacher that knows Misono is an omega and that's where the raws leave off.
It's not that Misono is going around just fucking everything with a penis it's literally just prejudice in omegaverse-- like always lol It's obvious that the only person he wants to be with is Hirose and that Hirose is protective of Misono. I guess they are just wanting to make sure before they do something permanent like become a pair lol
close call but to be honest the end of chapter 9 is a bit worrying, something is going to happen apparently because (spoiler)
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they end up together and look happy but while the seme is at the swim training a guy speak with the uke and then goes away with him. The chapter end with the seme watching a picture of the uke going away with this suspicious guy. Till now no rape but, for me, there's something fishy.

read the raws and to say the least, don’t waste your time. the swimming coach fingers the omega and almost has sex with him. then this other alpha comes in the picture later on in the story and makes the omega suck his dick like wtf. and then ANOTHER dude is coming in the picture so who knows what’s about to happen. i understand he can’t control his heats but jesus. every other day the omega is in heat it seems like. idk it irrates me.