One Ok Rock, stylized as ONE OK ROCK, is a Japanese rock band, formed in Tokyo, Japan in 2005. The band currently consists of Takahiro Moriuchi (vocalist), Toru Yamashita (guitarist, bandleader), Ryota Kohama (bassist), and Tomoya Kanki (drummer). They have been playing many different styles of music, with songs ranging from alternative rock to emo to post-hardcore to pop rock.
The band's name comes from "one o'clock", the time that the band used to practice their music on weekends. They chose to play at one o'clock in the morning because it was cheaper to use the rehearsal space during such hours. However, noticing that the Japanese language made no distinction between R's and L's, "O'CLOCK" transformed into "O'CROCK" or "O'KROCK", which later transformed into "OK ROCK". In addition, One Ok Rock can be expressed as "10969" (wan-ō-ku-ro-ku). This band makes their music in Japanese, English and mainly in a mixture of both of the languages.