Eir Aoi is a singer-songwriter. After releasing videos on Niconico, she made her major debut with SME Records in 2011. She released 13 singles, 4 albums, and 2 greatest hits albums with the label.

After a two-night farewell concert at Nippon Budokan, she went on hiatus due to poor health in November 2016. In February 2018, it was announced that she had signed with SACRA RECORDS to release her fourteenth single.

She credits herself as simply "Eir" for compositions and lyrics. Her real name is Yui Aoyama (青山由依).