Rythem is a Japanese pop duo consisting of singer-songwriters Yui Nītsu (vocals/piano) and Yukari Katō (vocals/guitar), who formed the group while still in high school. With their unique blend of acoustic pop and folk, the duo debuted with the single "Harmonia" in 2003, which reached number 29 on the Oricon charts and was used as the ending theme for the anime series Naruto. Their first album, Utatane (2004), peaked at number 6 on the Oricon charts, while their second album, Mugen Factory (2006), reached number 17 and included the hit single "Houki Gumo ホウキ雲," which peaked at number 12. The third album, 23 (2008), reached number 18 on the Oricon charts and featured the single "Kubisuji Line (首すじライン)," which peaked at number 24. Another notable song, "Butterfly," served as the opening theme for the anime D.Gray-man. Their final non-album single, "Gyuttoshite ぎゅっとして feat. 常田真太郎(from スキマスイッチ)," was released on July 29, 2009. After eight years of activity, Rythem announced their disbandment in 2010 and held their final concert on February 27, 2011, marking the end of their career as a duo.
