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 (vocals), Toru Yamashita (guitar/leader), Ryota Kohama (bass), and Tomoya Kanki (drums). They have been playing many different styles of rock music, with songs ranging from alternative rock to emo to post-hardcore to pop rock.
The band's name, ONE OK ROCK, comes from "one o'clock", the time that the band used to practice 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, they changed "O'CLOCK" to "O'CROCK" or "O'KROCK", which was then separated to become "OK ROCK". In addition, ONE OK ROCK's name can be expressed as "10969" (wan-ō-ku-ro-ku). This band sings both in English and Japanese like some other J-rock bands.