Shotaro Hidari (左 翔太郎 Hidari Shōtaro, is a self-dubbed "hardboiled detective", though considered "halfboiled" by others to his dislike, who dresses in the style from the 1940s and wears a black fedora/trilby made by the Windscale design house. He has a sharp intuition and may even figure out the culprit behind a crime before having Philip confirm his or her identity. Vowing to ensure that no one ever feels sad, Shotaro took on the job as the protege of Futo's private investigator Sokichi Narumi. However, during the Begins Night incident, an investigation into a mysterious organization led to Shotaro meeting Philip prior to Narumi's death, leaving Shotaro to continue in his stead, Narumi passing on his white fedora to Shotaro, his final words telling Shotaro to "grow into a man worthy of wearing it". A year later, refusing to let his mentor's death be in vain, Shotaro works to stop the Dopant crime wave by being the man on the street, contacting his various informants and transforming into Kamen Rider Double by providing his body for the formation. Shotaro takes the role of Kamen Rider Double very seriously and with great pride as the name "Kamen Rider" was given to them by the citizens themselves. As such, he tries to make a good name for Kamen Rider Double. Shotaro's body was never meant to handle Gaia Memories which is why he initially had trouble maintaining their Rider form when Philip's power was evolving. However, he has proved to be able to overcome these obstacles to become worthy of being the true Kamen Rider Double. Another goal he has throughout the series is to live up to Narumi's expectations, which he finally does in the battle with the Utopia Dopant. During the battle, he wears Sokichi Narumi's white fedora, having finally believed in himself that he has become worth of wearing it.
In the movie Kamen Rider W Forever: A to Z/The Gaia Memories of Fate, Shotaro receieves his mentor's Lost Driver. With the T2 Joker Memory, Shotaro can become Kamen Rider Joker allowing him to fight on his own Before Philip becomes one with the Earth after saving Wakana and defeating the Utopia Dopant, he manages to come across the Lost Driver and gives it to Shotaro as a farewell gift, allowing Shotaro to continue fighting as Kamen Rider Joker after his disappearance using the standard Joker Memory. About a year later, Shotaro continues to fight doing the best he can to protect the city of Futo when a gang of kids calling themselves EXE becomes a threat. However, he is soon reunited with Philip as they, once again, protect the city as Kamen Rider Double.
Philip is a mysterious young man who possesses the true Gaia Memory , referred to as the "Chosen Child" whose powers were used to create the Gaia Memories and whoever possesses him would rule the world. After being rescued by Shotaro and Sokichi Narumi from the Museum, receiving his new name from the latter, Philip aids Shotaro in order to atone for being used as a puppet by his captors. He investigates Dopant activity through his ability to access the Gaia Library and its Infinite Archive metaphysical realm and Akashic records in the form of white room filled with an endless number of books on an endless number of bookshelves. However, due to having no memory of his life before being rescued and the need to keep his location secret from the people Shotaro rescued him from, he usually spends his time in the Detective Agency's secret hangar, reading about common topics that he finds interesting. Sometimes his unintentional focus on a topic will turn into an obsession that overwhelms him until he knows everything about that subject, often getting in the way of ongoing investigations. He fights the Dopants with Shotaro, allowing his consciousness to separate from his body to fight as Kamen Rider Double, providing the Gaia Memories for the right side of Double. He eventually discovers that his real name is Raito Sonozaki, the third child and only son of the Sonozaki family, after his mind was altered by Satoshi Yamashiro under his father's wishes for Raito/Philip to have no memory of his name and family (which explains why the pages on his family were torn out when he was attempting to look them up), as well as discovering that his mother is Shroud. It is also revealed to him that Raito actually died twelve years ago in a freak accident, and he was revived as an avatar for the true Gaia Memory to save him. After he is joined with the Gaia Memory once again, he becomes a part of Wakana until Shotaro is able to overcome his fear and pull Philip's mind (along with the Cyclone Memory) and body (with the Xtreme Memory) out of ClayDoll Xtreme. However, this event makes Philip's body unstable to the point that should he transform into Double, again, he would break up into data and completely be absorbed by the planet. Saving their final transformation to save Wakana and fight the Utopia Dopant, Jun Kazu, Philip has Shotaro promise to him that he will still fight for Futo even if he is gone. After Kazu is defeated, Philip bids his final farewell to Shotaro as he fades away once the transformation is ended. Before he left, Philip left Shotaro a gift containing a Lost Driver belt and the blank book he used to access the Gaia Library containing a message thanking Shotaro and asking him to continue to protect Futo. However, after Wakana learns that Philip sacrificed his own physical existence to save her, she initiates her own Gaia Impact to bring back the Xtreme Memory which slowly reconstructs Philip's physical body. Before returning, Philip has one last moment with his family who tell him that they will be watching over him. Once revealing himself a year after his physical form is completely restored, Philip resumes protecting Futo with Shotaro as Double. He, as well as his cat Mick, are the sole surviving members of the Sonozaki Family.
Philip was named by Sokichi Narumi after the fictional detective. His name is alternatively spelled as "Philippe" in the aura that is produced when he accesses the Gaia Library. His real name "Raito" is pronounced similarly to the English word, as he forms the right side of any Double formation.
CycloneJoker
CycloneJoker is Kamen Rider Double's primary form, colored green and black and is accessed from the Cyclone and Joker Memories. In this form, Double's kicks are powered by wind, increasing the damage and adding cutting potential. This form's Maximum Drive finisher is a called the Joker Extreme, during which a tiny controlled tornado lifts Kamen Rider Double into the air before Double's body splits down the middle as the halves reach their target in a fashion. A variation of this attack involves Kamen Rider Double jumping off the back wheel of , allowing for faster acceleration upon descent.
HeatJoker
HeatJoker is the first Half Change form used by Kamen Rider Double when he appears in the Kamen Rider Decade film, colored red and black and is accessed through the Heat and Joker Memories. In this form, Double can throw flaming punches by means of the Heat Memory's powers.[3][4][5][6][10] This form's Maximum Drive finisher is a Rider Punch called the Joker Grenade, during which Kamen Rider Double somersaults in mid-air, then HeatJoker's body splits down the middle during descent as the halves each hit the target with elementally energized hooks.
LunaJoker
LunaJoker is the first Half Change form used by Double within the series, a gold and black-colored form accessed through the Luna and Joker Memories. In this form, Double has the ability to stretch his right limbs by means of the Luna Memory's powers. This form's Maximum Drive finisher is a Rider Chop called the Joker Strange, during which LunaJoker splits down the middle, the Luna half makes four copies of itself, and all five Luna halves execute rapid-fire karate chops on the target, and then the Joker half strikes the target with an energy powered chop.
CycloneMetal
CycloneMetal is a green and silver-colored Half Change accessed through the Cyclone and Metal Memories. In this form, Double can wield the Metal Shaft by means of the Metal Memory's powers. When swung, the Metal Shaft creates blades of wind by means of the Cyclone Memory. This form's Maximum Drive finisher is the Metal Twister where Double spins around while swinging the Metal Shaft covered in an aura of wind.
HeatMetal
HeatMetal is the second form used by Kamen Rider Double, first appearing in the Decade movie All Riders vs. Dai-Shocker. It is colored red and silver and is accessed from the Heat and Metal Memories. In this form, the damage from the Metal Shaft is increased by fire. A common tactic used by Double is to turn around while changing to this form, using the Metal Shaft on his back to block enemy attacks. This form's Maximum Drive finisher is the Metal Branding , causing one or both ends of the Metal Shaft to ignite on fire and deliver a final blow to the opponent. A variation of this attack is the Steam Metal Branding, a tandem attack used in combination with Kamen Rider Accel's Engine Blade which is only seen in the Hyper Battle DVD.
LunaMetal
LunaMetal is a gold and silver-colored Half Change accessed through the Luna and Metal Memories. In this form, Double can wield the Metal Shaft by means of the Metal Memory's powers, using the Luna Memory's abilities to use it like a whip. This form's Maximum Drive finisher is the Metal Illusion where Double spins the Metal Shaft around to create golden rings that float around Double, before unleashing them upon the target all at once.
CycloneTrigger
CycloneTrigger is a green and blue-colored Half Change accessed through the Cyclone and Trigger Memories. In this form, Double wields the Trigger Magnum by means of the Trigger Memory's powers and is able to shoot out high compressed air by means of the Cyclone Memory's powers. This form's Maximum Drive finisher is the Trigger Aerobuster, firing multiple shots of pressurized air at the enemy.
HeatTrigger
HeatTrigger is a red and blue-colored Half Change accessed through the Heat and Trigger Memories. In this form, Double wields the Trigger Magnum by means of the Trigger Memory's powers and shoots fire blasts by means of the Heat Memory's power This form's Maximum Drive finisher is the Trigger Explosion, which fires a single constant stream of fire that completely melts the enemy. HeatTrigger is the only form of Double's that has attempted to perform a Twin Maximum, in which the Trigger Magnum blasts out a massive fireball that incinerates anything in its path.
FangJoker
FangJoker is a white and black form that Kamen Rider Double first uses to escape from Philip's captors during the events of the Begins Night as seen in Kamen Rider × Kamen Rider W & Decade: Movie War 2010. As the Fang Memory was designed for Philip, he and Shotaro's roles as Double are reversed in FangJoker, with Shotaro's consciousness transferred into Philip's body for the transformation. Because of this, when Shotaro speaks, Double's left eye flashes. This allows Philip to go out into the open and utilize Double in case Shotaro is not around to help. However, the transformation is extremely taxing on Philip's body, and he lost control of himself in this form during its first two uses. In addition, they cannot stay in the FangJoker form for too long due to Philip's weaker body. By activating the Fang Memory's horn between one and three times, FangJoker is able to summon a bladed weapon that forms on various portions of FangJoker's body. One time summons the Arm Saber on FangJoker's wrist to be used as a close combat weapon; two times summons the Shoulder Saber, which can be removed from FangJoker's right shoulder to be used as a dagger or boomerang-like weapon; three times summons the Maximum Saber on FangJoker's right ankle. This last Saber is used to perform FangJoker's Maximum Drive: the flying roundhouse Rider Kick Fang Streiser, in which a projection of the Fang Memory's head is shown "biting" the opponent when Double comes in contact.
Final Form Rider
During the events of Kamen Rider × Kamen Rider W & Decade: Movie War 2010, Kamen Rider Decade uses the "Kamen Rider W" Final Form Ride card and splits CycloneJoker into two separate iterations of Kamen Rider Double. When Decade uses the Final Attack Ride card, Double CycloneCyclone and JokerJoker alongside Decade can execute the Triple Extreme rider kick.
CycloneCyclone
CycloneCyclone is the green Final Form Ride form that Philip can control independently. In this form, another Cyclone Memory for the Body Side is produced and gains the power over wind. CycloneCyclone also gains a second Windy Stabilizer scarf on his left side.
JokerJoker
JokerJoker is the black Final Form Ride Form that Shotaro can control independently. In this form, another Joker Memory for the Soul Side is produced and gains the power of agility and strength. In Kamen Rider W Forever: A to Z/The Gaia Memories of Fate, Shotaro can transform into a similar rider called Kamen Rider Joker by using the T2 Joker Memory and the Lost Driver.
CycloneJokerXtreme
CycloneJokerXtreme is the evolved form of CycloneJoker accessed with the Xtreme Memory, linking it directly to the infinite knowledge of the true Gaia Memory through the iridescent band going down the middle of Kamen Rider Double's body called the Crystal Server . It also represents the perfect union between Shotaro and Philip, as they become completely one through the Xtreme Memory absorbing Philip and attaching to the Double Driver. Thus when either Philip or Shotaro speaks on their own, their respective side's eye flashes, they also appear together as soon as they end the transformation. The knowledge of this form allows Double to instantly analyze the opponent's capabilities. CycloneJokerXtreme's Maximum Drive is the Double Xtreme Rider Kick; after closing and opening the Xtreme Memory, a twister forms around Double that lifts him into the air to then accelerate him down towards his target. By using the Prism Memory in the Double Driver's Maximum Slot and activating its Maximum Drive as well as the Xtreme Memory's Maximum Drive, it enables CycloneJokerXtreme to perform a powered-up version of the Double Xtreme called the Double Prism Xtreme which extends the initial drop kick into bicycle kicks. In this form, Double wields the Prism Bicker which has its own Maximum Drives. Unlike the other forms of Double, CycloneJokerXtreme's motif also includes the letter X.
CycloneJokerGoldXtreme
CycloneJokerGoldXtreme is an enhanced version of CycloneJokerXtreme that appears in Kamen Rider W Forever: A to Z/The Gaia Memories of Fate as a result of strong winds affecting the Xtreme Memory. In this form, the Crystal Server turns golden with a set of insect wings that allows Double to fly. CycloneJokerGoldXtreme's Maximum Drive is the Golden Xtreme rider Kick.
Double uses this form again during the events of Movie War Core to finish Kamen Rider Core along side Kamen Rider OOO Tajadol Combo
CycloneAccelXtreme
CycloneAccelXtreme is a form that is only described by Shroud as being the ultimate form that can be attained by Kamen Rider Double. Rather than being a union between Shotaro and Philip, CycloneAccelXtreme is the union of Ryu Terui and Philip, as both of their physiologies make them immune to the attacks of the Old Dopant and the Terror Dopant. Shroud states that Ryu's hatred and rage is needed for Double to fight at its full potential. However, Ryu decides not to fight as part of this form after showing Shroud that they can fight with compassion rather than hatred.
Though not making a physical appearance in the series, CycloneAccelXtreme appears in Kamen Rider: Climax Heroes OOO where he is armed with both the Engine Blade and the Prism Bicker. While able to use the Engine Blade's Gaia Memories in his attacks, CycloneAccelXtreme uses the Prism Memory's ability to link Philip's three elemental Gaia Memories with the Accel Memory to perform his own version of Bicker Finallusion.
