His “illness” is mental illness
If you consider being gay an illness, than sure. Not long ago, only around 50 years ago other sexual orientations were treated as illness and many tried to 'cure' them. Not to mention how nad it was earlier. Electroshocks were for example one of the physicial ways, but those people during 'treatment' were taken to hell becuase of prejudism, lack of acceptance, brainwashing and they'd never turned out mentally healthy. Just like we see in this story. We are yet to acknowledge what really happened to Seungho and knowing how parents are able ruin their children psychically, I expect some very bad things going on.
Cavo don’t feel insecure about ur face we love you