
I wouldn't say Jiheon is manipulative. He just did what he could do because he cared about Jaekyoung and didn't want him to be hated on or living in regrets.
While that part does seem frustrating to some, it's actually one turning point that will make the story and their relationship progress in a different way than before. I /personally/ really liked that part.

It definitely will, 100%! One of Dash's strongest points is the character development (one of the BEST in Korean BL, imo), and you will surely feel that in future chapters. People who said the characters are annoying (either Jiheon or Jaekyoung or both) most definitely haven't read enough chapters to feel the development. Maybe they stopped at certain chapters without even bother to give them a chance, and I honestly think that isn't a fair judgement :')

??? No. MC only slept around when he was in the last year of college. After that, he sobers up and works diligently at Spoin. He does have rare hookups every once in a while, but that's way before meeting ML again. He NEVER sleeps with someone else after that.
It's okay to dislike MC with quite an "adventurous" past, but I personally don't care about it since it's just part of his past an doesn't really hurt his current relationship with ML.
I am at the part in the novel where they had their first sex. And I think maybe it’s just me but I don’t feel the butterflies. Not that I don’t like them, but it started just wrong. Like, they weren’t understanding each other and it’s Jiheon pushing for Jaekyong to participate in the olympics even if he already made it clear that he doesn’t want to. And then they had sex. Just to see who will regret more. Jiheon also felt like a real player. I think he is very manipulative. I don’t know. Jaekyong’s also not that nice of a person, but Jiheon really likes to push him to his limits. I’m pausing for now coz i feel a little stressed. Lol.