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.

However, shortly after the band played at Meguro Live Station on October 11, MASAYA left the band, causing kagerou to go on a temporary hiatus while looking for a new bassist. The group became active again after 喰耶 (Kuya) joined as the replacement bassist. Kuya didn't remain as bassist for very long, and left the band on August 25. Luckily, KAZU filled the bassist position almost immediately, and remained in the band for the rest of its existence. This lineup would be kagerou's most famous lineup. In December of 2001, kagerou and ムック (MUCC) held a four-date coupling tour.

kagerou had a busy year in 2002 with in-store performances and many more performances from spring to summer. They toured constantly and released "XII dizzy" in early 2004. They began a long tour that ran straight until April, took a break in the summer, and then released 落首 (Rakushu) in August, followed by another tour. In February 2005 the band went on their first overseas tour to Germany and France. They also appeared at the Rock im Park festival in Germany. In October, the band ended the year with a coupling tour with D'espairsRay across Japan and throughout Europe.

At the live of September 16, 2006, at LIQUIDROOM Ebisu, they stated their disbandment. On December 27 they released a final best album, 心中歌, followed by a DVD 蜉蝣最終公演 (Kagerou Saishuu Kouen), released March 28, 2007. They went to Europe for two final tours before their last live performance on January 8, 2007.

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