Comment by Kira on Monochrome Rumor - Chapter 45

From the hints we got so far.. I think the person he love betray him.. perhaps that person force original sihyeon to be a "plaything" for rich people and then blackmail him causing sihyeon to take illegal loan...

And that's most likely the reason why he has social anxiety because he's sexually harassed causing him to have temper issues and probably depression

SPOILER!
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His lover gaslighted him and drugged him for the rich to play with him hence he feels dirty when people are touching him

MC's ex lover Jahea (the blondy guy from another group) was jealous of him and used his feelings to make him miserable. He told MC to ask money from a loan shark and MC has to wh*** himself to pay his debt because his sister was hospitalized.
MC trusted his lover but was betrayed/blackmailed and used.

Jahea never loved Shiyeon back but he likes to have his affection. He has a complex of inferiority and MC is more like a trophy.

Now that Shiyeon is ghosting him, he's pis*** but it's refreshing to see that he has to make a move to have his attention when before he hasd MC in the palm of his hand.