I've been trying to look for answers in the comments but I can't find any can you explain how it's his fault? I don't remember much I picked this back up after a long time and I don't really wanna re-read
He tried and failed to kill the pink haired villain and botched up the protagonists kill because the pink guy came to save him.
Tbh i believe the kill would have failed either way since pinkhair already figured it out and was on his way back. I think the major difference is that Taeman might have been able to abort the mission and not get hurt and exposed had pinkhair come back earlier.
Seolho you son of a b***h this is all your fault!!!