........what happened to him ???? He's soooo adorably cute here!!! Why so cray cray now??...

I think he went crazy from this guy called dohyun its only a guess tho

True true, dohyun probably did some damage like rape and left the little cutie, which in turn gave him mental problems making him cray cray.
Man dohyun, why you gotta (possibly) do this!!! (っ°Д °)っ

Im pretty sure Dohyun never raped Sungho. And even thou Sungho didn't like it, it was still consensual because he would do anything to stay by Dohyun's side....I think a bad break up could have driven Sungho crazy.