I understand this and agree to an extent. My only issue is that current Ido's actions were influenced by first Ido's actions.
It makes you wonder if he would've made the same mistakes as the first Ido if he had no idea of how it ended the first time.
But then as you said, despite that current him didn't really do any harm so can we really hold this version of him accountable?? Idk man everything hurts including my brain
This reminds me of the question you’ll sometimes hear in college philosophy courses. “If you could go back in time and kill Adolf Hitler in his cradle, would you?”
Most people say yes. A few feel conflicted. They wonder if his future is really predetermined. Will he really become the same person even if his future is changed?
What if he were to become the adopted son of a loving Jewish family? What if the one who went back in time, raised him themselves while teaching him about world war 2 as a bedtime story… a story where “Hitler” was called by another name. If it was never revealed to be the child that the villain of the story was himself… if the time traveler waited until it was clear how the child Hitler viewed that “character”…
What if child Hitler thought of the “character,” who once tried to take over and ruin the world, as a scary man who was like a monster? What if he idolized the American soldiers who fought against him? What if he decided that someday he wanted to grow up to be a hero that protects everyone from the scary bad guys? ………..
…could you still kill him? Would it still be justified?

I feel like people are forgetting that this is sorta like two different timelines. Yes, the Ido and sejin of the first timeline did bad things to each other but this is a second timeline where the Ido and sejin got the memories of the first timeline couple as dreams, almost as if it was a gift from first timeline couple, so that they don't repeat the same mistakes. Second timeline Ido did nothing wrong and it feels wrong for him to be punished for first timeline Ido's mistakes.