Thanks, that's an exhaustive explanation.
And damn, I was hoping that the redhead guy had at least some redeeming qualities. Like, he's a generally shitty guy, but at least he would bother saving someone drowning. The actual development in the manhwa removes depth from both the redhead and Karhan - the former because he now has zero redeeming qualities, and the latter because it makes Karhan so ideal even fate is on his side - so you don't need to think twice about how to feel about either of them
We knew since like ch 10 that the redhead lied though (and that he was irredeemable because he cheated and immediately tried to neg her into staying) lol. His flashback from his POV was that he just found her already on the ground (though I do wonder why Karhan just. left her there...) and when he saw how loaded she was from the reward she gave him, he engineered 'coincidental' meetings to get her to fall for him because moneyyyyy.
So, he didn't go in the water to save her, but he did see a woman lying around and go 'uh wtf that ain't right'. Which is like. The bare minimum I guess, but we don't need multifaceted villains all the time, sometimes people are just shitty and it's fun to see them fail.
Karhan and Ilya are meant to be in the story, sure, but the chances of them reconnecting were slim. Without that fortune teller, Karhan would probably be engaged to that clout chaser Delota lady or whatever his crazy mom wanted and he would be doomed. Karhan's an ideal person sure, but it hasn't done him much good in life.