It looks like Rurouni Kenshin: Saisen is going to extend well beyond the Kyoto arc and delve into the Jinchu arc of the series as well. The Jinchu arc, as you might recall, had Kenshin facing the fury of his former wife’s brother, Yukishiro Enishi.
Enishi’s presence in the game was first hinted at in its debut trailer, released by Namco Bandai in December. Not only is Enishi himself going to be playable, a couple of his lackeys are in the game, too. Screenshots over at Famitsu reveal Inui and Otowa.