Possibility UwU

This manhwa is so good ╥﹏╥

But the possibility of the death of the ml's parents are probably not done by fl's dad.

There's a 50% chance that the father [fl's father] got there late after a big assassination or fight. Resulting in ml's parents dying. After Demon King arrived at the scene, killing all the left over enemies, ml comes out and sees Demon King drenched in blood. This results him thinking that the one who killed his parents was the fl's father.
NOTE: it also mentions that due to Ah woo's skills, fl's dad killed his parents [early chapters]. So with that in mind, the fight in this prediction probably started because they also wanted his[ml] skills for their own benefit.

If he and the ml's dad got along, it's not reasonable for them to kill each other. I mean it's not impossible. But if they had a good relationship, they'll be willing to help one another.
With that in mind, the fl's dad is the demon king. So it's reasonable for ml's parents to refuse his offer of using ml skills for next sect lead.

But this is just a possibility in my opinion and what I think.
(づ￣ ³￣)づ but im loving it so far