Nobuhiko Akizuki

Century King Shadow Moon (世紀王シャドームーン) is a character who serves as the primary antagonist in the Kamen Rider Series installment Kamen Rider Black. In almost all of his appearances, he is voiced by Masaki Terasoma, including the 3D short film Kamen Rider World, the 40th anniversary film OOO, Den-O, All Riders: Let's Go Kamen Riders, and the Kamen Rider/Super Sentai crossover film Kamen Rider × Super Sentai: Super Hero Taisen.

In Kamen Rider SD, he is voiced by Kaneto Shiozawa. Nobuhiko, Shadow Moon's human form, is played by Takahito Horiuchi.

Black
Shadow Moon is the alter ego of Nobuhiko Akizuki (秋月 信彦), who had been abducted by Gorgom to become one of their new kings. Shadow Moon is both the stepbrother and rival to Kotaro Minami, who had been abducted alongside Nobuhiko but managed to escape.

Like Kamen Rider Black, Shadow Moon utilizes the King Stone to transform and is armed with the Satan Saber, a sword crafted specifically to be used by the Century Kings.

He was weakened by Kamen Rider Black using the Satan Saber to slash the Kingstone. He was left inside the Gorgom Headquarters when his Kingstone exploded.

RX
5 years later, he mysteriously resurfaced to seek revenge against his step brother. This time, he wielded the twin Shadow Sabers, similar to the original Satan Saber, gained from the Crisis Empire. He was finally defeated by RX when he thrusts the Revolcane through Shadow Moon's Kingstone. He turned good shortly before he died and finally reverted to Nobuhiko.

Kamen Rider World
However, Shadow Moon would return once again as a villain in the debatedly non-canon 8-minute movie Kamen Rider World. This time, he was a giant and he was defeated by Kamen Rider J's Jumbo Formation.

Super Hero Taisen
Shadow Moon returns as a member of the revived Dai-Shocker under Tsukasa Kadoya and like all the other past villians, pretended to assist his plan to destroy the Super Sentai while wokring in cahoots with Dai-Zangyack to have the Kamen Riders and Super Sentai destroy each other. Once it is revealed that in fact it was Tsukasa and Captain Marvelous who were decieving them to stop their plans, Shadow Moon joins the fight against the heroes just to be defeated along General Jark by the combined efforts of Kamen Rider Black and the Hikari Sentai Maskman.

Super Hero Taisen Z
to be added

Kamen Rider SD
Shadow Moon: A member of GranShocker. The brother of Black RX and apparently a Kamen Rider himself. This version of Shadow Moon tries his best to be evil, but falls short of his own expectations. He is armed with the Satan Sabre and an unknown motorcycle (possibly a Road Sector modification). He is constantly teased by Black RX, whom refers to him as "Sunshine Moon."

In other media
Shadow Moon is one of the few villains in the Kamen Rider Series to be given an action figure, Sochaku Henshin figure, and a Super Imaginive Chogokin figure. He is also one of the few Kamen Rider villains to have a Rider Kick, without being a Kamen Rider himself.

Shadow Moon was also featured as the first Secret Rare card in the Rangers Strike Masked Rider Expansion Vol. 1 and the only character in the Dark Alliance group in the Masked Rider Expansion Vol. 1.

An alternate reality version of Shadow Moon appeared in the film Kamen Rider Decade: All Riders vs. Dai-Shocker.

King Stone
 The King Stone (キングストーン) is Shadow Moon's transformation belt. Embedded upon the center his belt is a green stone called the Stone of the Moon (月の石). Through this stone, Shadow Moon can telepathically communicate with Kotaro via his own King Stone.

Shadow Sabers
The Shadow Sabers (シャドーセイバー) are pairs of long and short swords manifested by the King Stone, this weapon was used as replacement for the Satan Sabre.

Battle Hopper
The Battle Hopper (バトルホッパー) is a living motorcycle created by Gorgom, made specifically for the upcoming Creation Kings Black Sun and Shadow Moon, programmed to be loyal to the strongest King Stone bearer. Battle Hopper was controlled by Shadow Moon via his Shadow Flash before Black uses his King Stone Flash to retake him from Shadow Moon. As a results, Shadow Moon attacks Battle Hopper with the Satan Sabre before Battle Hopper rams with the suicide attack and dies.