Shoutarou Hidari is the left hand side of Kamen Rider Double, but also a Rider in his own right as Kamen Rider Joker. A self-proclaimed "hardboiled detective," he dresses in a retro fashion based on late-1930s style, favoring fedora hats and waistcoats. He is often called 'half-boiled' by his friends, however, because he cannot fully shut out his doubts, was initially seen as inexperienced, often acts according to his feelings, and has difficulties making cruel yet necessary decisions, contrary to his hard-boiled aspirations. He later on becomes more respected though, as he proved himself throughout the series. He works as a private detective in the city of Fuuto.

(Source: Kamen Rider Wiki)