Well, it doesn't say it outright, but that's certainly the implication.
On the surface of it, the video merely depicts a duel of honor between a samurai of the Takeda clan (the four-diamond crest on red is unmistakable) and a sohei warrior-monk (likely from the Uesugi clan), but those last moments at the end clearly notes the true message of the trailer: The guys in the castle are assholes who shoot winning dudes in the damn back.
Then again, maybe the Takeda guy had it coming, because he forgot to bow before turning his back. I guess that would make them even.
There's not a lot of gameplay information in there, but you can of course check out my hands-on preview for that.