O21 (O To One) was a South Korean-Chinese girl group under Houxiu TV and FNC China. They debuted on June 20, 2016 with the single "Show Me". They disbanded in 2017 due to the THAAD issue.
- RuRu (루루) - vocalist, lead rapper
- Sona-K (소나-K) - sub-vocalist, main dancer
- Yuri (유리) - vocalist, lead dancer
- Jiyoung (지영) - vocalist
- Wei Yang (웨이양) - leader, visual, lead vocalist
- Lina (리나) - main rapper, vocalist