I'd say bad RNG, not a bug. There's a chance you might get Wind Blade Asiuma, there's a chance you won't. All RNG, although I usually get himce four times a week, or so.

yea there was a time at the beging that i got him atleast once a week but now not a single time for a whole month that jsut seems imposible

Its not that its just with the new frags they added for clearing survival trial stages there is a wider pool of rare ninja fragments to get so its just more likely you get other ninjas like the 100 puppet and pains etc

Got him 5 times during last two weeks. Just unluck.

hope it jsut bad luck cuz all im geting are the akatsuki members and rarely some pains