One Ok Rock (stylized as ONE OK ROCK) is a Japanese rock band formed in 2005, composed of Takahiro Moriuchi, Toru Yamashita, Ryota Kohama and Tomoya Kanki. They well-known from playing the theme soundtrack for Rurouni Kenshin live action movies. The band name, One Ok Rock, came 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 then was separated to become "ok rock".