This move is done in TwinSword4, and it might work in other sword modes, too. It's probably been done dozens of times before, I just felt like posting it because it looks cool. The actual attack ends at 330ish and leaves a lot of time for your own customizations.
Demo Settings

Press C
Space
Contract both pecs
Raise shoulders
Space x3
Contract knees
Lower shoulders
(OPTIONAL FROM THIS POINT ON, YOU'RE FREE TO DO WHATEVER NOW)
Space x2
Extend both wrists
P

This should cause Uke's pecs, arms and head to seperate. If you do the optional finish, his swords will clank together and the rest of his body will be perfectly intact. You could extend the knees and he would probably kick the arms away or something, but I didn't feel like it.

(Ignore the attachment, it doesn't want to go away.)

Haha, didn't bother to read the first half of the post, and just tried doign it in Toribash Vanilla; Obviously didn't work. My bad, I'll try it in twinsword and get back to ya *Foreheadslap*