I got confused when op said Olga's the one who stopped Zhenya and thought maybe I missed something from the novel cuz I don't remember something like that happened, Olga only came up after Zhenya tried to revive Taekjoo by fixing his airway then left after he realized it's the first time he got emotionally confused and panicked for killing someone, then Olga only came in after Zhenya left to treat Taekjoo.
Actually it's the story board creators who couldn't do their job right properly that's why the manhwa kept missing some details, Han is only responsible for the arts but there are other staffs who makes the raw sketches and panels and they're the ones to decide the flow of the story (most of the story are adaptations from a novel) and give to the artists so they can easily trace the sketches. And the story board creator of CA (especially the season 2 after Han switched company) just kept removing some most of the important details from the novel, it's beyond disappointing tbh.

SPOILER! Guys, trust me when I tell you that this is 100 times softer than the novel. The artist kinda changed a lot of things, but anyway... Zhenya reached a point where he unconsciously wanted Taekjoo dead, but luckily, he stopped before killing him. In the novel, it was Olga who stopped him, and right after that, Zhenya rested his head against Taekjoo's chest, near his heart, to hear if he was still alive ╥﹏╥