Responses
Yh and at the start of the story nobody was actually there to see the fight except from the fathers best friend who was fighting with him so they would have heard of this martial art that looks like a dragon but seeing it is different and they could think its just another dragon martial art and not the one that killed the demon
I think, the reason why they don't remember the arts is because his father shut himself off for years after the mc's mom died. Also the reason why they don't recognize the mc is because he was locked in the shed for 10 years and like when he was 5 smth he was pretty neglected, they also didn't introduce him to the murim so probably why they don't recognize him anymore and the arts. Only the old people who fought his father knew the arts, since they considered him a formidable person. (The demon sect also knew his father because he fought them and almost killed the leader i think?)