Portuguese and Dutch merchants already known about Japan by this point, so if Nobu wants to ally with actual gaijin one of them is more likely than say, French German Russia or Brits
And unlike other natives in colonial age Nobu is formidable opponent against any enterprising colonial powers...
I'm pretty sure that Matsuri actually did many streams in just underwear, and Mio is self-professed nopan (only when sleeping, but nobody believes just that)
Qin wouldn't assassinate such an useful idiot like Zhao King, and I doubt minister is also on Qin payroll, he struck me as typical egocentric power hungry guy, status quo suits him just fine.
So it's either Prince or Kaine or Shunsuiju or even new third party (pretty much every other kingdom is...
Finally we get confirmation what is the current year. So Riboku will survive and Qin would most likely lose next battle, or at least forced into stalemate. Also some guy got his arse butthurt and exploded I guess.
Riboku actually came back (or not yet exiled/disgraced) historically to defeat Qin in Fanwu albeit with pyrrhic victory, which in larger scheme only reduces Zhao's overall strength as Qin recovered fairly fast to conquer Han first. This may be the excuse the King finally needed to get rid of...