蜉蝣 (kagerou) were a Japanese rock band that formed in September of 1999 in Tokyo. 大佑 (Daisuke) and MASAYA were the band's original members, with Yuana joining as the guitarist a month or so later. The band performed their first live show together at CYBER on February 13, 2000. On April 4, their first maxi single, titled "Biological slicer", was released, and in May, 静海 (Shizumi) joined the band. With this lineup, kagerou performed many concerts around the country.