Or try this:
about this distance from Amakusa
jump and IMMEDIATELY do a fierce slash (A+B)
this is very important, -don't do the slash when you
falling from the jump-
Amakusa usually will be in block animation (if not he will jump, and don't worry the slash will hit him) and you as soon as
you feet touch at the pavement (and near the boss) DO A THROW
(A+B or B only, but I suggest tap A+B.)
repeat this until he die.
If Amakusa do the teleport, (often in the final round) just contiune do the same, distance, jump+fierce slash, throw etc..) untile die or the time run out.
If Amakusa do that move, block it and faster use a weak attack or -medium but long- (or a ground fierce slash if you have a ninja) to hit him.
I have successful tried this with all chara but Charlotte,Nakoruro have some problems because she have an high jump , remember the distance may depends of your chara jump type.