"Sleep" is a single by Japanese rock band Sid, released on March 3, 2010, by Ki/oon Music.
The two limited editions, A and B, include a DVD with the music video for the title track and footage of "Aikagi" at a concert of Hikari tour.
[2] Tower Records described the song as "vividly portraying the anguished feelings of love [...]" and praised the melody and vocals of Mao.
[5] Regarding the B-side "Utahime", CD Journal company said it is a dance-rock song with a "quiet and moving" charm.
[7][8] On Tower Records' Japanese Rock and Pop Singles chart, it peaked at number four, as well as on Billboard Japan Hot 100.