Alain (アラン Aran) is a young man who first appeared to be Saionji's partner before later revealed to be the son of the Gamma emperor Adonis. He seeks the Eyecons to examine their power, for reasons that have yet to be revealed. Javel has been sent by Adonis in order to help him, but after Javel disobeys his orders, Alain begins to hypothesize on what his subordinate's true orders are, as well as those of Adel. He steals the Mega Ulorder and Necrom Eyecon from his brother, and gains the ability to transform into Kamen Rider Necrom (仮面ライダーネクロム Kamen Raidā Nekuromu). Robin Hood has told Takeru that he sees that Alain follows his own twisted ideal of justice, just as every other person follows their own form of justice. After being framed for his father's death and unaware of his brother's treachery, Alain decides to take the throne from Adel while trying to adjust to life in the human world. He helps Takeru find Makoto and his human body in the Gamma World as he is honorbound after the two rescued him many times. On the trip back, Alain learns from Alia that the Demia Project is simply a set up for Adel's coup attempt and that Adonis is alive and well, but imprisoned in his mortal body. While he searches for his father, he learns why he and other Gammas are immortal and realizes why Takeru believes the Gamma World is a dystopia. Takeru ultimately saves Adonis but the reunion between father and son is cut short when Adonis sacrifices himself to save Alain from Adel's assassins. Alain promises to carry out his father's will in saving both the human and Gamma Worlds, but is distraught when he sees Adel kill his father with his own hands. As Makoto manage to catch up with Takeru and Alain, Makoto brings Alain back to his senses with a punch to the face, only to be fully snapped when Adel insults Alain for being as weak as their father. Back in the human world, Alain decides that he will seek to restore peace and happiness to the Gamma World by defeating his own brother. When Alain and his friends finds out that Adel's first victim before their own father was Takeru's father, Ryū ten years ago, Alain apologize Takeru for what his brother done to Ryū, but Takeru replies it was not Alain's fault, as he notes that Adel's madness was because of the death of Gamma royal siblings' mother, Alicia, which in turn that his older brother end up being manipulated by Gammisers. Once the Gammisers' reign of terror is finally over thanks to Ghost, Alain is now pardoned to return to his homeworld. While returning to his homeworld, Alain is accompanied by Makoto and Kanon, who decided to help him and his people restore his world's environment and peace, while Edith and Javel decide to stay in human world.
As Kamen Rider Necrom, Alain uses a brace called the Mega Ulorder (メガウルオウダー Mega Uruōdā) and Ghost Eyecons to transform. His primary form is accessed via the Necrom Eyecon, and his Omega Ulord (オメガウルオウド Omega Uruōdo) finishing move is the Necrom Destroy (ネクロムデストロイ Nekuromu Desutoroi), which can be used as either a Rider Kick or a Rider Punch. The Necrom Eyecon allows Alain to control others' minds, from Gammas to even humans, including two Eyecons he acquired from Javel. If he is ever defeated in battle with his Eyecon body destroyed, he can transfer his consciousness to another Gamma's body, transforming it into his own. Necrom can also make his body intangible to physical harm, but he cannot protect himself from electric-based attacks. However, as the Necrom Eyecon is still a prototype, Necrom's transformation is limited, which means he must summon Gammas and then absorb them (or absorb an enemy's energy attacks such as those from Gammiser Fire) in order to power himself to fight longer. Unfortunately, the Necrom Eyecon has an even worse side effect in that if Necrom unleashes his rage too much, the Eyecon could end up destroying his body. After Alain completes his training in Sanzo's Eyecon world, Necrom receives his own version of the Gan Gun Hand called the Gan Gun Catcher (ガンガンキャッチャー Gan Gan Kyatchā) which can also switch between Rod Mode and Gun Mode. Similar to the Sunglasseslasher and Deep Slasher, the Gan Gun Catcher can hold an Eyecon for Necrom to perform one of two finishing moves: the Omega Crash (オメガクラッシュ Omega Kurasshu) in its Rod Mode or the Omega Finish (オメガフィニッシュ Omega Finisshu) in its Gun Mode. Like his fellow Riders, Necrom has access to other "Damashii" forms depending on which Eyecon he inserts into the Mega Ulorder:
- Grimm Damashii (グリム魂 Gurimu Damashii) empowers Necrom with the spirits of the German folklorists where he is able to utilize the pen nib-like G Pen (Gペン Jī Pen) on his shoulders for offensive and defensive attacks. Unlike the other heroic Eyecon spirits, Grimm exists as two individual Hoodie Ghosts who each represent the reincarnated souls of Jacob and Wilhelm Grimm with blue eyes and orange eyes respectively within their Eyecon world but merge into one single Hoodie Ghost with green eyes when summoned into the real world. This Eyecon temporarily possesses Yuichi Katagiri, the elder brother of Akari's university professors. When the Brothers Grimm fight with each other due to their contrasting personalities, they disrupt Ghost Grateful Damashii's powers which results in Igor stealing the Grimm Eyecon for himself. While in his possession, Igor can harness the power of said Eyecon through his Proto-Mega Ulorder by using the G Pen to manipulate the environment and its inhabitants around him into resembling one of the Brothers Grimm's fairy tales and their characters. Soon after the Grimm Eyecon is recovered and the Katagiri brothers reconcile with each other, the Brothers Grimm bring Takeru into their Eyecon world to thank him for his help while Jacob reminisces about his true reason of writing fairy tales for enjoyment and reconciles with Wilhelm as well.
- Sanzo Damashii (サンゾウ魂 Sanzō Damashii) empowers Necrom with the spirit of the Chinese Buddhist monk (accompanied by his three mythical disciples from Journey to the West: Sun Wukong, Zhu Bajie, and Sha Wujing) where he is able to utilize the bladed wheel-like Gokourin (ゴコウリン Gokōrin) on his back as a projectile. This form's Omega Ulord has two variations for Necrom to use: summoning Sun Wukong's legendary flying cloud for various purposes, such as transportation or a finishing move, or riding the Gokourin like a flying hover board to ram into enemies. This Eyecon temporarily possesses an idol singer named Honami (ホナミ). When Alain is unable to use the Sanzo Eyecon's power, he is sent by Sanzo into his Eyecon world to be trained by his disciples so that he can not only earn his cooperation but also unlock his Damashii's true potential, such as being able to summon the disciples to aid him in combat.
While possessing a Gamma body, Alain could also use his Necrom Eyecon in any of the other Kamen Riders' Ghost Driver belts, turning the wearer into his brainwashed servant. He first uses it on Specter, turning Makoto into Necrom Specter. However, only someone who is very close to one of Alain's brainwashed Ghost Driver users can break his spell.
In Ghost Re:Birth: Kamen Rider Specter, Alain obtains a golden color-lined version of Toucon Boost Eyecon called Yujo Burst Eyecon to transform into Yujo Burst Damashii (友情バースト魂 Yūjō Bāsuto Damashii, Friendship Burst Damashii), powered by the power of friendship.
Alain is portrayed by Hayato Isomura (磯村 勇斗 Isomura Hayato). As a child, Alain is portrayed by Yūsei Itō (伊藤 悠成 Itō Yūsei).