In a joint effort between Watanabe Entertainment Co. Ltd. and Sony Music Records, an audition was held in 2013 to find strong vocalists. Six girls, were chosen and began their indie activities as Little Glee Monster (リトル グリー モンスター) in May of 2013.

The group gathered attention by showcasing their extraordinary vocal talents in collaborations with other artists and TV appearances. They covered songs from notable bands and artists such as BUMP OF CHICKEN, Southern All Stars, and MISIA and even covered the Disney hit “Let It Go” from their 2013 film Frozen and “What Time Is It?” from High School Musical 2 from the High School Musical franchise.

Little Glee Monster released their first self-titled mini-album Little Glee Monster on March 16, 2014 and later made their major debut with the single 放課後ハイファイブ (Houkago High Five) in October.

Despite debuting with six members, the group went through a lineup change, with current members being Karen, MAYU, Serina, manaka and Asahi, and former members LINA, YUKA and Maju; LINA and YUKA withdrew from the group in 2013, while Maju withdrew in 2017.

The group has also attracted some attention from western artists, as they collaborated with Grammy winning acapella group Pentatonix on the track “Dear My Friend”, marking a first original Japanese track for the acapella band. The two would later collaborate once again for the track “Midnight In Tokyo” which would be included on the album the deluxe edition of Lucky Ones.