pls note it's him who marked an omega. In this ABO version, those marked can't be with another person just like Keith in <Kiss me, Liar>. If the other person isn't marked then they will react to other's pheromones. Check <Kiss Me, Liar> side story where Yeonwoo's mark was gone and he reacted to another extreme alpha's pheromones. Here, Chase isn't marked he can still do it with anyone. You're right at some point that "he's so sensitive cuz his pheromones have been piling up and he can't release them through sex".. but that is surely not because he marked another omega. :))
Yeah I know it’s the alpha that marked the omega. But I meant in the sense that sometimes in omegaverse some alpha reject other omegas & can only be with their marked omega. Sometimes it cuz they’re fated. Like in Kiss Me Liar, Keith couldn’t hook up with other people he tried but he wouldn’t get hard lol like their body subconsciously rejects others. I think his body is unconsciously noticing him, that’s why he asked the manger if they were all alphas/betas. When he jumped in the pool to save him I think he reacted to his pheromones a bit. If you see the scene again he stopped for a brief moment as if he noticed soemthing. That’s why I’m assuming he might have tried having sex but couldn’t
so i assuming he probably hasn't been able to have sex with other omegas since he marked him years ago. Thats probably why he's so sensitive cuz his pheromones have been piling up and he can't release them through sex. lol i can already see the trope of him going into heat & then the omega is gonna get caught up