Kamenrider v11

    After being kidnapped by the cult Gorgom in the night of their 19th birthday, step-brothers Kotaro Minami and Nobuhiko Akizuki were submitted to a cyborg surgery with the purpose of becoming the candidates for the next Gorgom's Century King. Kotaro escaped before the brainwashing, with help from his foster father, and turned against Gorgom. He soon finds out the horrific truth from his step-father: Gorgom originally killed his true parents and, since both Kotaro and Nobuhiko were born on the day of a solar eclipse, referred as "Black Sun" and "Shadow Moon". Kotaro, taking on the name of Kamen Rider BLACK, was determined to rescue his step-brother from Gorgom while protecting Japan. However, later in the series, Nobuhiko emerged as Shadow Moon to fight Kotaro with the survivor becoming the next Century King.

Kamenrider Black RX

    Having a new life 5 years after the destruction of Gorgom at the hands of Kamen Rider BLACK . Kotaro Minami has gotten a job of a helicopter pilot in a business owned by the Sahara family. Later that night, Kotaro was captured by the Crisis Empire and asked to join them. When Kotaro refused, his Kingstone was destroyed and he was thrown into space where the sun's radiation altered his Kingstone and he evolved into Kamen Rider BLACK RX. With his new powers, he battles the Crisis Empire and thwarts their plans to take over Earth. During the half of the series, Shadow Moon mysteriously returns to seek revenge against him, shortly after, Shadow Moon was finally defeated when he thrust his light saber through Shadow Moon's Kingstone and turned good shortly before he died and finally turn back to Nobuhiko. In the finale, he was helped by the 10 veteran Kamen Riders to destroy Crisis Empire once and for all.

RX's other forms:
Kamen Rider BLACK RX was the first Kamen Rider to have multiple forms: Robo Rider and Bio Rider. The concept of "multiple form changing" Riders would be repeated with Kamen Rider Kuuga (2000), who has many different armor types, Kamen Rider Agito (2001), Kamen Rider Kabuto (2006), Kamen Rider Den-O (2007), and Kamen Rider Kiva (2008). Kamen Rider Blade's Jack Form, Kamen Rider Hibiki Kurenai, and Kamen Rider Faiz Accel Form are seen as initial upgrades rather than form changing. Form changing is best describe as alternating back and forth between forms to adjust to different situations.

Robo Rider:
He gained this form in Episode 15. RX 's armor becomes bulky and more robotic-like, with black and yellow coloring and his belt resembles a gearbox. During his duration as the "Prince of Sadness", both his strength and defense are enhanced. He is also unharmed by explosions or projectile weapons. The only downsides are that he moves slower than BLACK RX as well as possessing semi-robotic movement, slowing his reaction time. His weapon is the Vortech Shooter, an energy firing pistol.

Bio Rider:
He gained this form in Episode 17. BLACK RX's armor becomes much sleeker, blue and silver all over and his belt resembles a single Kingstone belt. During his duration as the "Prince of Anger", his speed is enhanced. He can also transform into water for escaping traps or attacking enemies while not getting hurt in the process. His weapon is the unbreakable sword, Bio Blade.