This Kamen Rider Skull (仮面ライダースカル, Kamen Raidā Sukaru) is a version of Sokichi Narumi (鳴海 荘吉, Narumi Sōkichi) from an A.R. world, and is the Decade version of both Skull, and Kamen Rider Double.
His card mysteriously ended up in Tsukasa's possession but sealed, It was used (without Decade's powers) after the battle with Super Shocker by automatically unsealing itself and summoning the A.R Skull to Shotaro.
He met the prime reality Shotaro Hidari, Philip, and Akiko Narumi after Tsukasa Kadoya handed Shotaro a with Skull's image on it. This Sokichi Narumi came through a dimensional wall, praising Shotaro as well as (indirectly) giving him closure before returning to his world.
- Height: 205 cm
- Weight: 110kg
- Punch: 2 tons
- Kick: 6.5 tons
- Maximum Jump Height: 45m
- Maximum Running Speed: 100m/6.3s
Through the use of the Lost Driver and Skull Memory, Sokichi transforms into Kamen Rider Skull. Skull is unique in that besides wearing a white tethered scarf he also wears a white fedora. Skull's motif is that of a human skull and the letter S. Kamen Rider Skull's primary finisher is the long range shooting attack Skull Punisher (スカルパニッシャー Sukaru Panisshā), the Maximum Drive ability of his Skull Magnum. Kamen Rider Skull also appears as one of the Kamen Riders summoned by Kamen Rider Diend's Complete Form and his Gekijouban Card. In this appearance, his Maximum Drive attack is a generic Rider Kick, similar to Rider 1's famous somersault and kick attack, but with a purple swirling energy around Skull's right foot.
- Gaia Memories - USB-like transformation items and power-ups.
- Lost Driver - Transformation belt
- Skull Magnum - Gun
- SkullBoilder - Personal Rider Machine/Motorcycle