No need. I didn't read it either, but I still understood it lol. I mean, throughout the chapters, they give you context about what the mc was like in the past—why he's there and why he's going through in the present. I don't like the original Sadistic Beauty; I found it boring and sometimes irritating. Still, if you read the original MAYBE it'll change your perspective on the characters. There are people who read the original, and after reading this side story, they say that Minho deserves everything that happened to him. I’ve only read this side story, and I think Minho is a good protagonist—a 'bad person' sure—but one with a backstory where, in his own view, he’s 'paying for his sins'. I didn’t want to spoil it for you.
I used a translator to write this, so please excuse any mistakes.
Thank you for this heads up dear, it helps a lot. I added this to my list. (づ￣ ³￣)づ
If i read this, should i read the main story too or no need? Pls tell me. Thank you