
can someone tell me why is the top mad at the mc?

He’s Mad because he approached him with the intention to write a character for his manga based on him/his characteristics. But then he fell for him and they were really in love. But then top found out that he was using Him as material for his manga and felt used. They broke up and stopped talking for years and now are reunited.

ik this is fiction but, is this kind of bullying really happens in south korea? it's so extreme

Yes, sadly there are a lot of things like this happening even right now in south korea
Some peoples lives are being ruined because of this thing called deepfake that's been happening a lot.
The kdrama "The Glory" is based off many true stories from south korea if you want to know abt them then watch this:
https://www.youtube.com/watch?v=30dKS39GnXg&t=294s
And you can watch the uncencored version here: https://open.spotify.com/episode/2xP6mimFqmhvpXs4koD0St
The deepfake videos are very serious and some people even k!ll themselves because of it...
Videos mentioning deepfakes:
https://www.youtube.com/watch?v=1HuOrrznBvs&pp=ygVrcm90dGVuIG1hbmdvIE5ldyBOdGggUm9vbTogTWlkZGxlIFNjaG9vbGVycyBEZWVwZmFrZSBWaWRlb3MgT2YgTW9tLCBTaXN0ZXIsIENsYXNzbWF0ZXMgSW4gJ0h1bWlsaWF0aW9uIFJvb20%3D
This one mentions it too:
https://www.youtube.com/watch?v=cyPfoo6W48Q&rco=1
For all the purpotraiters of these crimes: (︶︿︶)=凸 Go to jail in hell!
Hope this helps~
he's been dreaming of this since god knows when