Shotaro Hidari (左 翔太郎, Hidari Shōtarō) is one of the two main protagonists of Kamen Rider W. He is a private investigator of the Narumi Detective Office who transforms into the left-side of Kamen Rider Double (仮面ライダーダブル, Kamen Raidā Daburu) with Philip on the right-side. Alone, he transforms into Kamen Rider Joker (仮面ライダージョーカー, Kamen Raidā Jōkā).