1. You do know Sangwoo was also a like yandare
2. If Hayan was not a yandare she would be boring as f***. Like nobody would like not even me, so the fact that the actor gave her a like personality makes her more exciting and better then a boring mage girl like have read TOO many boring mage girl.
A yandare one is more enjoyable for me oh and also if you don't like her you just f***ing leave and never come.