how it all happened

Trying to convince hiccup father to see that dragons can be good but it went horribly wrong, he was sent to death but managed to escape his fate but now he was cursed when he meet a man know as Muzan kibutsuji.

Now roaming world for 900 years along with toothless by his side, they eventually come to Japan and they start learning all about demon slayers and other demons.

Httyd x demon Slayer crossover

How to train your dragon x demon Slayer crossover