serious spoilers!!!
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Honestly, it's quite complicated
Short spoiler if you don't want everything spoiled: the ml kinda moves onto seeing the mc as his own person that's not seoho and grows to like him as himself, hinted that it's becoming likely that he'll choose him as his current self
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More serious spoilers: it appears that MC wasn't reborn as seoho, but died (if i remember right, i think the accident was staged¿) as a young boy and was the perfect vessel for the broken pieces of Seoho's soul (his soul was broken because he did smth forbidden to save/help ml live), so he currently only has 1/3 (I don't remember the exact details sorry) of the soul which is why he has his scent but no memories or anything else, so technically it's arguable whether that soul piece has changed him to be more like Seoho or he's authentically only Min-chan personality wise.
I hope i was clear enough and everything important is accurate if you choose to read it, personally it's understandable to feel a bit frustrated at the start because of how ML acts about the whole Seoho thing, but he definitely gets better and it's quite interesting, although I'd recommend waiting for season 3 cause season 2 ends on cliffhanger
at the start? Absolutely and definitely. He even refused to use Min's name and constantly called him Seoho, talking about memories, being lovers, etc, completely disregarding (and actually not even understanding) why Min was getting mad at him
Eventually when something happened that led to ML acknowledging Min as his own person, we can start seeing that he actually has developed feelings for Min himself that aren't just some projection of his feelings towards Seoho, although (spoiler spoiler) when he finds out that when all soul pieces are collected and transferred into Min to completely turn him into Seoho, ML was genuinely distressed and worried about Min disappearing to the point where he didn't show any joy or excitement at the thought of Seoho returning and there was a dialogue between ML and smth like hallucination/dream Seoho about ML living without him and moving on (but also about living in either reality with Min or in the Illusion with Seoho, he chose Min). Towards the end of season 2 both characters express that they're "seeing each other" or at least "exclusive" BUT!!! most of this happens in season 2 and they get together together towards the end, so we don't really have a strict conclusion on ML's feelings for Seoho, but personally i think he's slowly learning to let go and move on after suffering for so many years. Personally i hateee ex lovers or reincarnated lovers, but this one doesn't make it out so horrible for the MC and i think portrays both of their issues quite well, there are many discussions about death and moving on in different situations that help ML mature and grow, and MC to be a bit more open and vulnerable again. But like i said, sadly, things were just starting between them and then it just ends on cliffhanger.
Also omg this became so long, in short he is definitely stuck on his lover for a longgg time but in a way it's also because he's been all alone for 1500 years wandering stuck with the betrayal from Seoho, in a way, he genuinely didn't know who he would be without Seoho and any feelings for him whether positive or negative, because it's like there was nothing left in him but pain, and if that person who is responsible for the pain is gone?? Then he wonders who he is without it and why did he have to survive and suffer for so long
I hope i answered your questions if you have more, feel free to ask!!

guys can someone spoil me? Is this a story where ml is stuck up on past lover and just likes mc cus he has part of his soul or whatever? Or is mc actually the past lover and has his memories