Back Number (バックナンバー, Bakku Nambā) is a Japanese rock power trio formed in 2004.
The person who was in charge of the bass at that time wanted to quit and then joined Kazuya Kojima, who is a childhood friend of Shimizu and is now the current bassist.
Hisashi Kurihara, who was the drummer of that band and also went to the same high school as Kazuya, was recruited into back number and has been in charge of the drum since then.
Since 2005, voluntary live performances were held annually in November (until 2007), following the release of the demo CD.
On February 18, 2009, the band released their first mini album, Nogashita Sakana, and became HMV push item "HOT PICKS", TOWER RECORDS push item "Tawareko Men" for the first time, selected as power play of FM station and Sony Ericsson CS commercial song, the band then was widely known throughout the country.
On May 27, Tawareko, a back number free live with HMV as the co-ownership was held at SHIBUYA-BOXX, and more than 500 people joined, which exceeded the capacity of the regular entry.
In June, the band finished a tour at the Ferrari Temple Park Outdoor Stage in Isezaki City with a crowd of 500 people.
After that, the band also positively appeared in events such as "SAKAE-SPRING", "MINAMI WHEEL", "TREASURE", "MUSIC CUBE" all over the country, school festival, install alive, etc.