[EnerPrime]

So I had an idea about this movie recently. They keep showing Kotaro as Black instead of Black RX, despite the fact that this is most likely supposed to be the same Kotaro without any dimensional shenanigans.

But I got to thinking what if, in the years since Black RX (the show), Kotaro figured out how to transform into regular Black again and now saves the stronger Black RX form for use in dire situations, like all the Heisei Rider's super modes?