Also, what I like about the first couple, is that you don't get bored of them acting too sweet, clingy with each other. Their petty banters are cute, and that's just me. You can choose to skip them if you don't like their dynamics and read the other couples instead, same as dropping something you don't like reading. No need to push the hate or negative stuff on others. And just enjoy reading what the author writes. :)

Bruh, i dont really get why you guys have to fight over who's right or wrong between Dojin and Hyesung. I mean, they aren't perfect people, and not all character development are great or fast. I don't really get the hate for both of them as they both have their own unique personality or character. I don't compare them to how the second couple or tertiary couple are. In reality, not every couple have the same level of relationship, same quirks, or closeness. Couples fight whether it's big or small, petty or serious.
Don't act like people don't get insecure or jealous from time to time. Yeah, they made up from the obstacles they have in the past, but that doesn't mean they could just change their couple dynamics. And when I say by couple dynamics, is how Hyesung acts snobbish or cold towards Dojin, and Dojin being possesive, clingy towards Hyesung. You see, that's how the author wrote about their characters, they are different from Dojun or Heeso. Hyesung is the type of uke that has like a cat personality or tsundere. So if you have a pet cat, you know how cat can be, and their owners still love them even though they just don't give a care about you do. So other owners get a dog cause they can't stand a cat snobbishness.
Dojin on the other hand, can be really needy for love because of the type of attitude/personality Hyesung has, and he can't show it other than have sex with him, which i know a lot of people here are annoyed about, he is bad at communicating, same as Hyesung, and i don't know if he ever treat his uke to date and stuff, then he acts possessive and childish sometimes, but you know both of them lack in dating and romantic aspect in their relationship because of how they started being just physical and also their past experiences as well. So it won't just change drastically, some people tend to do the same mistakes in their relationship. And that's what the author is showing here.