This is what I think happened. I wonder what author has cooked up.

I honestly think seo in had a twin brother. This twin brother most probably didn't like yeongwoon for whatever reason or was just a bully. (Honestly I think he hated yeongwoon cause seo in was getting "stolen" by yeongwoon. Idk I have seen a lot of plots were twins are portrayed to have this weird relationship where one is a bit possessive over the other.) I believe that when this twin and his gang or whatever beat up yeongwoon he suffered major injuries which made him not be able to do judo which is why he stopped doing judo (this is an assumption) Now since he has such major injuries and probably was in the hospital he could file a complaint to the police which would make headlines and seoin's mom didn't want this. So she gave huge amounts of money to yeongwoons father to settle this. That's honestly what I think happened. Maybe i could be wrong.