Shotaro Hidari

Shotaro Hidari is the left half side of Kamen Rider Double but also a rider of his own self as Kamen Rider Joker. He is a self-dubbed "hardboiled detective", though considered "half-boiled" by others, who dresses in the style of the late 1930s. He works as a detective in the city of Futo.

Vowing to stop anyone that makes his city cry, Shotaro took on the job as the protege of his mentor Futo's private investigator Sokichi Narumi. However, in the investigation of a mysterious organization, which led to Shotaro meeting Philip, Sokichi is shot to death leaving Shotaro to continue in his stead. Refusing to let his mentor's memory 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 combination. Shotaro's body however was never meant to handle Gaia Memories which is why he had trouble maintaining their Rider form when Philip's power was evolving. However he has proven to overcome these obstacles to become Kamen Rider Double CycloneJoker Xtreme.

Shotaro appears to be the one who came up with the names of Double's finishers, as demonstrated in episode 16 when he decided to call Fang Joker's Maximum Drive Fang Streiser.

His surname is literally translated as "left" (左) and his Gaia Memories provide the left side of any Double formation.

Personality
Shotaro's basic personality is an homage to the fiction character of Philip Marlowe, as is his sense of being a hard-boiled detective. Shotaro is decisive and intuitive making him a remarkable detective even without the help of his partner. At times Shotaro's emotion and dedication to the choices that he makes causes him to come to blows with his partner and others. He cares deeply about his clients, his friends, and his city and will do anything in his power to protect them.

Shotaro is a contrast to his partner Philip, showing great emotion and intuition as opposed to Philip's cold and logical thinking. Because of his emotional side, he is capable of understanding the emotions and actions of others. While Shotaro usually tries to be the serious one out of his group he is often the one that is made a fool of by his friends. 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 has a habit of flicking his left wrist in the air before and during battles, similair to Takumi Inui (Kamen Rider Faiz)'s habit of flicking his right wrist at his side

Abilities
In combat Shotaro shows great fighting skills outside of using Gaia Memories, even in a weakened state of becoming an old man due to the Old Dopant. He has also shown a great skill in locating pets easily, moreso than finding people, first seen when trying to locate a cat not knowing it was a trick and finding Mick.

Gaia Memories
The Gaia Memories (ガイアメモリ) are mysterious USB flash drives imbued with the powers of the Earth itself. Originally created with funding by the Sonozaki Family, these Gaia Memories end up in the possession of Shotaro and Philip, and can only be used through the Double Driver. Two can be inserted into the Double Driver, allowing Shotaro and Philip to transform into Kamen Rider Double. Shotaro's left-half Memories called Body Memories (ボディメモリ) determine the type of attack or weaponry that Double uses.


 * Joker Memory (ジョーカーメモリ): The Joker Memory, also known as the Trump Card Memory (切札の記憶), allows the user to increase fighting potential, becoming the Skill Warrior (技戦士). When used, half of Kamen Rider Double becomes the black Trumping Left Half (切り札の左半身). When the Joker Memory is placed in the Maximum Slot on the Double Driver, it allows Double to execute the Joker Extreme Rider Kick. Shotaro can also use the T2 version of the Joker Memory with a Lost Driver to become Kamen Rider Joker.


 * Metal Memory (メタルメモリ): The Metal Memory, also known as the Steel Memory (鋼鉄の記憶) or the Fighter Memory (闘士の記憶), empowers the user with great strength, becoming the Superpowered Warrior (怪力戦士). When used, half of Kamen Rider Double becomes the silver Fighting Left Half (闘士の左半身).


 * Trigger Memory (トリガーメモリ): The Trigger Memory, also known as the Sniper Memory (銃撃手の記憶), turns the user into an expert marksman, becoming the Gun Warrior (銃戦士). When used, half of Kamen Rider Double becomes the blue Sniping Left Half (狙撃手の左半身).

Kamen Rider Joker
Through the power of the T2 Joker Memory and the Lost Driver, Shotaro uses the power of the Joker Memory to its full potential. When the Memory is placed into the Maximum Slot, Joker executes either a Rider Punch or Rider Kick Maximum Drive. This form is lost after the Joker Memory is taken by NEVER but after Philip dissolves into data and becomes one with the Earth, Shotaro finds in the present Philip gave to him, the Lost Driver from the incident and he uses his original Joker Memory for him to become Joker again. However, one year later, Shotaro is overwhelmed by the newly formed EXE group until Philip returns.

Lost Driver
With Shotaro unable to use the Double Driver he uses a Lost Driver he received from Skull instead to transform. This Memory Driver was lost in the battle with Kamen Rider Eternal, but recovered by Philip, which he gives to Shotaro. To transform Shotaro places the Joker Memory in the Memory Slot to transform into Kamen Rider Joker.

Gaia Memories

 * T2 Joker Memory: The T2 Joker Memory was one of the 26 T2 Gaia Memories and the first Gaia Memory used by Kamen Rider Joker, both for the transformation and Finisher. However, the T2 Joker Memory was lost when Eternal was able to defeat Joker using the T2 Unicorn Memory to execute his own Rider Punch Maximum Drive, then it was destroyed when Golden Xtreme Double destroyed Eternal.
 * Joker Memory: After the T2 Joker Memory was destroyed and Philip dissolved into data completely, Shotaro uses the original Joker Memory in place of its successor.