In the Black RX World, which will conclude the series, Tsukasa will meet Kotaro, and the season will end on August 8th with the movie and the bid gathering of all Riders plus ZWEI.
And two Natsumi's? One next to Yuusuke, the other next to Otoya with googles on.
The girl with Otoya does not look like Natsumi at all...she does not even have stockings....