Question: Not Alone, is Zhang Liyin's which number overall single, Zhang held a showcase to support the release of the single, which was held at the Century Theater in Beijing, EXO members Tao and Chen were guests, Exois a South Korean-Chinese boy group based in Seoul? 
Sentence (from "Exo (band)"): Exo (Korean: 엑소 ; stylized as EXO) is a South Korean-Chinese boy group based in Seoul.
Relevant evidence: Yes