Mind that mindblowing announcement Square Enix and Yahoo! had for today that would "change Japanese history"? Yeah, about that...
Turns out it was just a browser-based game for the Sengoku series, known as Sengoku IXA.
And unlike most browser-based Sengoku games in Japan, where you have to pay for them, this one is free!
The official site's here, just in case you're curious.