I'm pretty sure that's incomprehensible Japanese screaming, much like how a lot of heavy metal is incomprehensible English screaming. If you could actually make it out, I'm sure it means something.
That ending was foreshadowed right at the beginning. There really was no other way for it to end, was there?
If you liked the drama and trickery aspects, you might like Spice & Wolf. It has a lot of that dynamic, applied to trade deals and medieval European(ish) economics. Significantly less action and life-or-death situations, though they are there.