My Secret Guard Has Countless Previous Owners

Ren Shuangbo is a miracle doctor, the kind who can compete with the King of Hell for his life. He has a surly personality and relies on his mood to treat illnesses and save people... Isn't that a standard feature of a miracle doctor? I accidentally showed kindness and picked up a hidden guard. Well, it works great. Wait, why do you have so many previous owners! Where is the promised loyal dog?