Their second single 'Hanabi' was released on May 31, 2006, earning the band their first appearance on the Oricon top 10 chart with a number 5 debut.
This was their major label debut with Epic Records Japan of Sony. On March 15, 2006, the band released their first single, SAKURA, produced by Masanori Shimada. As they were then performing with three members, the band did a cover of Yuzu's single, 'Natsuiro' ( 夏色 'The Colors of Summer'). Yoshioka was the younger sister of one of their classmates she entered as the main singer and the band took on its present-day form. In those days, Mizuno and Yamashita planned to make a group with a female lead vocalist, which would be an unusual sound for the street performances they were doing. In November 3, 1999, Yoshioka joined the band. At first, they did covers of Masayoshi Yamazaki. Yamashita and Mizuno formed their band on February 1, 1999, and began performing live on the street not taking it too seriously, they named it 'ikimono-gakari' after their shared experience in first grade.
Yamashita later noted that he really wanted to be a 'blackboard monitor'. In 1989, Mizuno and Yamashita met by chance while they were in the first grade they were both put in charge of being Ikimono-gakari ( いきものがかり), who are caretakers of the school's plants and animals.
