it is one of the new techniques he learned in the 2 year break dedicated (?) to/for ace. i don't exactly remember the mechanism behind it.
You know I can't either i do remember him using it during his battle with hordy. I think that's the first time we saw the red Hawk punch. he may have been still grieving at that time for ace. if you watch the anime when he does the punch the first time there is a flash between him and ace. it flashes back and forth between the two of them until he makes contact with hordy like an ode to ace
ohhh! Honestly I don't even remember this!! ;;;;;
We've been on a hell of a journey so we seen a lot of things it's all right if some of that manages to slip through the cracks I think that's how oda manages to get over on us and his wonderful use of foreshadowing
im still hella curious about how it works tho haha ┗( T﹏T )┛ I'll just reread everything until i find sthg i guess? x'))
I'm guessing here but it's just like all of Luffy's anger after Ace died is what causes the same Flames that remind him of ace. again just a guess
And if you find out how then please update me too (づ￣ ³￣)づ
This is what i got from reddit and it makes the most sense...
I always assumed it was friction between his haki-coated fist and the air that created it, kind like what happens when you enter the atmosphere at relatively high speed. Is that correct or is it more like Sanji's diable jambe? I am asking because sometimes in the Anime(which might be what induce me in error, since I dont read the manga and it might be different there) it looks like the fire starts before the punch is launched, it ignites when he trows his fist behind, and then it launch forward
this is an interesting theory hmmm
how was his arm in flames?