Maybe jihwa snitched on him when they were younger.
Actually I think quite the opposite happened. He has mentioned before he is the only one who knows, and even when he was hurting/drunk and others wondered what he was talking about he did not say.
I think SH & Jihwa were just found messing around as young teens and that’s why SH father said Jihwa also had the “disease”
maybe seungho took the blame for it? bc if they got caught in the act, then both of their families would've punished them harshly. yet, jihwa probably only got his top knot cut off whereas seungho was basically tortured. plus, didn't the doctor say that it was a "contagious disease" and that jihwa also "caught the illness? if they were caught in the act together, then it wouldn't make sense that jihwa "caught" the illness from seungho.
(i wanted to explain why i think seungho wasn't able to love/care for jihwa, but it's too hard for me to put in words lmao)
I feel so bad for jihwa. BD really captured his heartache and desperation. It seems like he wanted to give SH a second chance, but with this rejection I’m sure he is going to go along with the assassination with Nameless and Min.
Now what I’m wondering is why does SH love/care about NK and not Jihwa? And I really think none of them know, not even SH himself. & that just adds salt to injury because Jihwa knows SH very well, his past, his trauma and has send he wants to help him heal in way and NK just comes in and SH completely changes with almost no effort in NK, in a way Jihwa was never able to reach.