Can anyone tell me where exactly the Kagehide is located? I've been looking all over Seki but I still haven't found any. I've check Nether Den of Needles but I've had no luck.

Try Burial Mound of the Preserved in Nether Seki.

Thank you so much. I was able to find them there.

so the kagehide is on bronze??? sliver??? or gold??? i have been hunting 8 runs in normal(Burial Mound of the Preserved in Nether Seki) but still no luck...
is it higher chance to run in hard or hell???

The Kagehide is from a GOLD ???, in preserved.

I tried hard mode and hell mode, with no substantial difference in drop rates, so just stick to hard,