Spoiler
There's no cheating and the MC will start falling for ML around the halfway mark of the story.
Well ML will join spoin, MCs company purely because MC is there. He'll soon find out that MC is an omega because of his pheromones that are apparent only to ML.
ML joins MCs company on the condition that MC be his on field manager. Since ML needs to also do ad campaigns to maintain income and bring profit to spoin, ML who is initially uninterested in this, agrees to do so on the condition that MC fulfill one of his wishes every time he does an ad campaign.
When ML and MC begin their manager - athlete relationship, MC wonders why ML wants to quit swimming after the Olympics. This is one of the main reasons why he doesn't sign with Kavva because they want him to continue swimming and not quit.
The relationship grows during this time and ML acts like a child a lot and MC has to indulge him a lot more even though he really doesn't want to. There's a whole subplot with ML and his friend who is supposed to be his 'lover'. MC figures out he is jealous ML's friend and he maybe likes ML but he's not sure.
They also have a whole reality show around ML where his main thing is showing how awesome his hyung is.
ML's next big goal is winning the Pan Pacific championships and around this time sometime he confessed to MC that he likes him. MC tells him not to talk about it further and they leave it at that.
Some other stuff happens in between but I forgot about those and then MC tries to put distance between them and it fails. Finally MC tells ML to participate in the olympics to prevent the regret that he himself had about not being able to participate.
ML tells him that if he sleeps with him he'll participate. He doesn't actually believe MC will and he'll be shocked when MC actually agrees. They have sex and that officially begins their sexual relationship.
After that they regularly have a lot of Dub con sex which is restricted to only once a week because MC gets tired but ML is as exepcted a horny gremlin.
Eventually MC gets pregnant, they get together, they get married and have a boy child Jin after.
The side stories are cute and do a better job of characterising the ML than the main story. They go for vacation in the philippines sponsored by a reality show which records their time there. The baby - dad interactions are pretty cute. And iirc he gets pregnant again. I haven't read after that.
I read the novel and I honestly hate the ML's character.
He acts like a child and basically kinda forces MC to have his way or he gets angry and fussy