One Ok Rock (stylized as ONE OK ROCK) is a Japanese rock band formed in 2005, composed of Taka, Toru, Ryota, and Tomoya. Originally a five piece band, guitarist Alex left the group in 2009.
The foundation for One Ok Rock began when Toru Yamashita, then a high school student, wanted to start a band. He told his friend Ryota Kohama, a fellow member of the hip hop dance group Heads, to learn the bass and asked Alex Onizawa to join. After seeing Taka Morita perform in a cover band, Toru insisted that he join. Drummer Tomoya Kanki had been playing with them since 2006, but only became an official member when they debuted in 2007.
The band's name, ONE OK ROCK, comes from "one o'clock", the time that the band used to practice on weekends. However, noticing that the Japanese language made no distinction between r's and l's, they changed "o'clock" to "o'crock" (or "o'krock"), which was then separated to become "ok rock".
...that Taka had an eye problem during their Jinsei×Boku= tour and had to get a shot to cure it instead of surgery due to being on a tour.
...that Kimishidai Ressha (キミシダイ列車) have been played live in 2009, there is a record titled with 'Untitled' released together with Around The World Shounen.