- Yajima Maimi (矢島舞美) (°C-ute)
- Tokunaga Chinami (徳永千奈美) (Berryz Kobo)
- Natsuyaki Miyabi (夏焼雅) (Berryz Kobo)
- Okai Chisato (岡井千聖) (°C-ute)
Mellowquad was announced in February 2013 at a special event for the SATOYAMA Movement. The group name comes from the idea of a rich prosperous ocean and the attributes of fairy mermaids, and the fact that there are four members. The members were chosen to have their independent powers come together as one to present a powerful and magnificent performance, like that of a quad-core processor. They were formed alongside the groups Dia Lady and HI-FIN to be part of the "Hello! Project SATOUMI Movement", a movement with the aim to remind Japan of their beautiful oceans and beaches, and the need to keep them clean and healthy, similar to the "Hello! Project SATOYAMA Movement" that puts focus on the countryside.
- [2013.08.07] Lady Mermaid / Eiya-sa! Brother / Kaigan Seisou Danshi (レディーマーメイド / エイヤサ!ブラザー / 海岸清掃男子) (Dia Lady, Mellowquad, HI-FIN)
Compilations / Other
- [2013.12.11] Hello! Project - Petit Best 14 (#16 Eiya-sa! Brother)