Kamen Rider Black to Black RX: How Things Were
There was the only one time in Kamen Rider history where one character starred for two different seasons, each one was a continuation and that was the Kamen Rider Black season. Kotaro Minami is both Kamen Rider Black and later, Kamen Rider Black RX.
Kamen Rider Black was a dark season, one considered by some to be the best season ever. IMO it was too dark for my taste, quite depressing for me and all but it still is one of my favorites as I grew up with him in my mind. So it was like a remake of Kamen Rider 1 but not really. The similarities were that he was captured by an evil organization (in here, it was called Gorgom and the first not to use foot soldiers in weird suits and it was a satanic cult), forcibly turned into a cyborg and he turns against them. He however must rescue his foster brother Nobuhiko Akizuki who later became Shadow Moon which becomes the point of conflict. Before that, he had to challenge that extremely arrogant and badass villain Bilgenia who was really the most cruel villain to be ever made for the show! The whole plot focused on the Century King where either Kamen Rider Black (Black Sun) or Shadow Moon will succeed the "Creation King" of Gorgom when one of them dies, sort of like the survival of the fittest. Everything focused on letting go of the past for a better future. It was a pretty bittersweet one. Most of the characters thought he died when he had lived on.
Eventually Kamen Rider Black RX was probably written in response to the success of Kamen Rider Black. So in a sense, Kamen Rider Black would have 98 episodes if we count Black RX in and that would be the same number of episodes as the first Kamen Rider. Compared to Black, Black RX had a more positive thinking Kotaro Minami, a lighter storyline but with more badass villains in my opinion in the form of the Crisis Empire. This season for me was better because it wasn't too serious nor was it slapstick but had a well-balanced script IMO. He had new allies, each one for me was interesting from his girlfriend Reiko, to Joe who replaced Shadow Moon (and Shadow Moon did return for a short time) up to the lovely Kyoko who could control water. The multiple forms were written into the script rather well and well, it was nice to have Tetsuya Matsui as General Tasmadder after he showed himself as the evil Bilgenia in the previous series. It seems to wrap up the Showa era rather well except leaving the plot hole behind the Crisis Empire's real identity as well as the Great Leader himself. But it did its best to wrap things up and introduce new stuff for the Heisi era.