Comment by Mimi on Monochrome Rumor - Chapter 125

That the evil bf was that guy from the other boy group who argued with himbut it's been so long since we seen him that I can't remember how he looked like.

Sanyu has some relationship with Jaeha (OG Sihyeon's sh*tty boyfriend). There was a time when Sanyu and Jaeha almost debuted in the same group. They were together all throughout their trainee days. Basically, Jaeha wants to see Sihyeon's expression if one of his members sees him in this condition. You know how OG Sihyeon hides his suffering from his members and is afraid they'll find out. So, Jaeha, being the twisted person he is, decided to bring Sanyu, whom he knew personally, to Sihyeon and open Sihyeon's blindfold so that Sihyeon can see Sanyu in front of him.

Sanyu's POV when he heard Sihyeon ended up in hospital:
When Sanyu found Sihyeon blindfolded, he was clearly aware of what state of mind Sihyeon was in and that he didn’t want to hear anything. He even knew that Sihyeon wouldn’t want to talk about it. Yet he calmly told Sihyeon that they should return to the dorm and talk it out. Even after all that, if he was still concerned, he should have taken the car keys or at least caught hold of him that day (basically, he believed he's a bystander who contributed to his Sihyeon's suffering by doing nothing). The next thing he heard about Sihyun was that he was in the emergency room. He felt his heart and bones ache to see him lying alone and cold. Just when he thought that it was all over, like a lie, he miraculously revived the next day. It was from that day on; everything Sihyeon did made him regret it. He also noticed the change in personality, tone, and even habits. Although they had the same pale face, it was like he had become a completely different person.