Tokyo Metro (東京メトロ, Tōkyō Metoro^?) is one of two rapid transit systems making up the Tokyo subway system, the other being Toei. It is the most used subway system in the world in terms of annual passenger rides.

Tokyo Metro is operated by Tokyo Metro Co., Ltd. (東京地下鉄株式会社, Tōkyō Chikatetsu Kabushiki-gaisha^?), a private company jointly owned by the Japanese government and the Tokyo metropolitan government.

The company replaced the Teito Rapid Transit Authority (帝都高速度交通営団, Teito Kōsokudo Kōtsū Eidan^?), commonly known as Eidan or TRTA, on April 1, 2004. TRTA was administered by the Ministry of Land, Infrastructure and Transport, and jointly funded by the national and metropolitan governments. It was formed in 1941, although its oldest lines date back to 1927.

The other major subway operator is Tokyo Metropolitan Bureau of Transportation (Toei) which is owned solely by the government of Tokyo. Metro and Toei trains form completely separate networks. Prepaid rail passes can freely interchange between the two networks (as well as other rail companies in the area), but fares are assessed separately for legs on each of these systems and regular ticket holders must purchase a second ticket, or a special transfer ticket, to change from a Toei line to a Metro line and vice versa. Though, most Tokyo Metro (and Toei) line offer through service to lines outside of central Tokyo run by other carriers, and this can somewhat complicate the ticketing.

Tokyo (東京, Tōkyō^?, "Eastern Capital") [toːkʲoː], English /ˈtoʊki.oʊ/; officially Tokyo Metropolis (東京都, Tōkyō-to^?), is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of the world. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family. Tokyo is in the Kantō region on the southeastern side of the main island Honshu and includes the Izu Islands and Ogasawara Islands. Tokyo Metropolis was formed in 1943 from the merger of the former Tokyo Prefecture (東京府, Tōkyō-fu^?) and the city of Tokyo (東京市, Tōkyō-shi^?).

The Tokyo Metropolitan government administers the 23 special wards of Tokyo (each governed as a city), which cover the area that was the city of Tokyo, as well as 39 municipalities in the western part of the prefecture and the two outlying island chains. The population of the special wards is over 8 million people, with the total population of the prefecture exceeding 13 million. The prefecture is part of the world's most populous metropolitan area with upwards of 35 million people and the world's largest urban agglomeration economy with a GDP of US$1.479 trillion at purchasing power parity in 2008, ahead of New York City metropolitan area, which ranks second on the list. The city hosts 47 of the Fortune Global 500 companies, the highest amount of any city.

Yui Aragaki (新垣結衣, Aragaki Yui^?, born June 11, 1988) is a Japanese idol, model, actress, singer, seiyū and occasional radio show host of Ryukyuan ancestry.

She is particularly recognized for her beauty and her movie projects.

Aragaki's career began when she appeared in the junior fashion magazine nicola. Upon learning that the magazine was looking for a new face, Aragaki's sister turned in an audition profile for her. Aragaki won the Grand Prix and officially became an exclusive model for nicola or a "nicomo". In 2001, her fellow nicomo Ayako Enamoto nicknamed her Gakky.

Aragaki expanded her modeling career into gravure in 2004. She also appeared in variety shows and commercials; she is best remembered for her TV advertisements for Pocky. In 2005, she graduated from the magazine and subsequently acted in the TBS drama Dragon Zakura alongside fellow Japanese idol Tomohisa Yamashita and actress Masami Nagasawa, marking her breakthrough in show business. Since Dragon Zakura, Aragaki had been cast in various dramas such as Gal Circle and My Boss, My Hero. Despite graduating from 'nicola', she still appears in the magazine occasionally. She currently holds the record of appearing the most number of times as its cover girl.