Fr, kinda cliche but it still good. 
If ya wanna know Imma drop the spoilers.
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Currently the premises of the story between MC, ML and White hair dude is what ya mentioned. ML is son of a chaebol (it's already obvious) while white hair dude has a beef with ML. White hair has a hyung who died and I believe he keeps on thinking it was ML's fault when actually that Hyung died of illness.
MC reminds the white hair dude of that Hyung, so basically his thinking of him as replacement. White dude is absolutely cray cray btw, coz at the end he choked MC and almost killed him coz MC doesn't wanna be with him coz MC already like ML.
After that the transmigration concept will be the main focus  basically where in the first part of the story and the real one will come later. Lmao but it's still your typical story ya might figure it out later as well                                             
                                                Thank youuuu for the spoiler, I'm loving thr fact that they stayed on theme.i would've gone mad if it's really not so typical because this really circled arounf and made fun of the typical romance.... I'm loving this (●'◡'●)ノ
Also you said itd by part right? Is the novel complete, can ou drop it for me if you're not busy. Thank you so much (づ ̄ ³ ̄)づ                                            
                                                Yeah kinda by part coz it actually ended when MC went back to reality and felt like the side stories is where they got together. Might just my understanding coz MTL isn't good you gotta figure it out along the way coz there's still no official English version nor fan translation of the novel..
Here's the KR novel,  https://booktoki469.com/novel/7368968?stx=%EC%84%9C%ED%82%B7+%EB%B8%8C%EB%A0%88%EC%9D%B4%EC%BB%A4&book=%EC%99%84%EA%B2%B0%EC%86%8C%EC%84%A4                                            

		
No wdym kill. What in the world of kdrama is this. Don't tell me he's a son of powerful ceo/gangster/political shts, or maybe he killed a past lover that second lesd kept on picturing mc into.... Mygoodness Σ(  ̄□ ̄||)