I think you misunderstood. I think the bottom wanted his parent dead since he hid the murder weapon (the bloody pins). He's a manipulator through and through and is very calculated. Like he knew the guy would come to him not the bride hence he wore a bridal outfit and put rouge on his lips. You really misunderstood the plot.
THAT'S EVEN WORSE THAN THE TOP WTF
Yeap, he is worse. It's a very toxic story but it's the whole point of the story. You actually don't have to like it, it's meant for you to feel unpleasant emotions. And this work does it magnificently.
SO YOU'RE SAYING THE BOTTOM DOESN'T EVEN LIKE HIM. AND THE FACT THAT HE'S ONLY DOING IT JUST TO SEE THE DESPERATION GUILT IN HIM(TOP) WHAT. EVEN WORSE IS THE TOP KILLED THE BOTTOM PARENTS JUST SO HE WOULDN'T LEAVE? GNG WHAT. THE WHOLE PLOT IS WHILE.