
So, Seungho has realised that he is homosexual since very young.
Somehow that fact got discovered by his father, and his father treat him like he got a disease.
Father think that homosexuality is disease/sickness.
Father can’t go to shaman because homosexuality have nothing to do with ghost or god or spirit.
Father can’t tell the doctor what exactly the disease is because he don’t want people to know that his son likes man.
So, father would caged Seungho inside the house as to be re-educated to stop being homosexual, and to make him back to “normal”.
That of course would stress Seungho out so much.
Once he reach adulthood, he is allowed to go out of the house, that’s when he start going crazy as a retaliation toward his father...

I was thinking about a theory that someone came up with
Before you continue reading #TW#
So the theory suggest that suenhgo was raped at a young age, because of his father who sold his own son in order to save his own skin, or to get what he wants (i think it was a position of power or something) , and as such treated his son as a prostitute.
(and by "sold" I'm mean the sex-slave kind of sold.)
The links below are where I found the theory, you should definitely read them, you will understand the manhwa way more.
https://bebebisous33analyses.wordpress.com/2020/10/13/painter-of-the-night-yoon-seunghos-secrets/
https://bebebisous33analyses.wordpress.com/2020/09/05/painter-of-the-night-hearsay-part-1/
https://bebebisous33analyses ur.wordpress.com/2020/10/13/painter-of-the-night-yoon-seunghos-secrets

Reading this I almost get convinced...
But, then it doesn’t represent why the young Seungho with flushing face and hick-ee on his neck looks bright and he seems happy? It was when the father brought him to the doctor...
From my POV, that young Seungho looks like he just “made love” with someone he like or something... and get caught by the father. But at that time he maybe not afraid of his father because he was currently in adrenaline rush of a thinking “as long as I have the one I love, I can do anything”.
....
So at that time, I believe Seungho was already experienced sex with a man, but it was not a forced sex, rather was a consensual one. (As the doctor said, that time he saw Seungho, the young lad looks bright, healthy, and doesn’t look sick. But after the father locked him in the house, Seungho became sick).
But, after that time, Seungho got locked inside the house, and whatever happened after he got locked is definitely the cause of his anxiety, nightmares and ptsd.

I get what you're saying, and you might be right Idk, but what I meant is that his father sold him after their visit to the doctor (when he was locked in the house), and that is what caused his ptsd.
And I'm still not sure if the bruises on his neck is a hick-ee or just a bruise because of the way his father was holding his neck.
" something must have happened while he was forced to stay home" it better not be what I'm thinking, or else gonna lose my sh#t. :D