I think you're just unlucky because i got him full by just using 100 protection vials

the rng is hell if try to do just one skill. Better remove protection for one more and give it a try like this. But at some point it is cheaper to do the last sb with frags.

true, in special when people lock what they get gold instead of locking only when they get the important parts first, i know someone fully bt naruto except... his passive, the thing that makes him truly broken... and ofc he ran out of protec, just cuz he locked every time he got a gold

You could also, use "Exchange" in "Recruit" to get his fragments for moon scrools (it is long process I know, but it is an option).

You could speed up this process if you get that skill to +1 using vials and protection, and then get it to +2 with fragments.

yeah i have done that with wrist arrow, it also didn't want to upgrade to gold

I needed absorbtion seal from the start but i couldn't get it

same as me. for my naruto 6p it took me 500+ protection just to get that * Y+1 dodge passive