>>1961465It's not just you.
That model for some reason has fucked up wrist and arm twist bones.
They just don't do anything.
But instead of just doing nothing, because of the way MMD works, they're rotating the elbow and wrist bone weights FROM where the twist bone is, which is why it's fucked up looking.
So any motion that requires arm/wrist twist bones will have that problem.
As far as I know, they are unusable unless you go in and fix them in PMXEdit, which I don't know how to do in that program.
You may, but I don't.
The default Miku Append model works 100% fine with the motion, because the model actually has twist bones that work, unlike the Miku Halloween model.
I thought it was because of bone names, but I just looked and they're pretty much exactly the same.
The bones just flat out do nothing.
I'm pretty sure the guy that made that video manually fixed the motion, or there's some way of fixing it that I'm not aware of.
But to temporarily fix it and get it presentable looking, just delete all the keyframes on the arm_twist_L, arm_twist_R, wrist_twist_L, and wrist_twist_L bones.
It won't look the same as the video, but it'll look "close enough".
