Fuguki's kinda like Hinata (normal)

Gains +this by X.X% each time they lose X% of health. Basically, it's an invisible buff, as opposed to scaling or add on buffs. It's just added on, kinda like healing tips

Except, I'm pretty sure, that if he were to regain hp, he'd lose X.X% of said buff

Fuguki works like Earth Main with steel body, like Naruto Ninetails chakra or like Ay 3rd (with chakra instead of hp).

You don't see the boost but you will notice it when happens.

o ok does he lose it if he regains HP like above said???

yes when gets healed his boost gets reduced consequently.

well thats pretty useless tbh..........

He's not buffing, Hinata clearly gets tougher the less hp she has, Fuguki just dies and as he's constantly firing his Mystery, it's clear he's not getting stronger.

If he's at 10% HP he should be 110% stronger but he's not.

works exactly like naruto ninetails chakra.

Put him with mei/darui, water enhancement and mifune and you'll see the difference between the damage he lands at 100% hp and the damage he lands at 5% hp.

also remember that 100% more ninjutsu doesn't mean 2x damage.