虹 by L'Arc~en~Ciel

"Niji" (虹, "Rainbow") is the eighth single by L'Arc-en-Ciel, released on October 17, 1997. It reached number 3 on the Oricon chart. It was their first release after Sakura's arrest and Yukihiro joining as the band's support drummer (he officially joined on January 1, 1998). The title track was used as the opening theme of the Rurouni Kenshin movie Ishin Shishi e no Requiem, making them the only artist to contribute more than one song for the franchise. The single was re-released on August 30, 2006. The song is one of the band's signature songs, often played at the end of concerts.