Tekken 8 | Heihachi Mishima 

It's explained in the story mode expansion update which if you want to check that out 👍🏾

@@Rromantiq Is this even canon? If yes, then damn you Harada

@@sonicdash9652 They're retconning a lot of stuff now and making everything even more confusing but yes it is canon now. Apparently Akuma shooting a fireball at Kazuya when he dropped Heihachi in the volcano was enough of a distraction for him to not see that Heihachi was saved by a monk