Sion (시온) is a South Korean singer under SD Entertainment. She is a member of the girl group SATURDAY and a former member of LIPBUBBLE where she was known as RyuA (류아).
On November 11, 2016, Sion was revealed to be a member of LipBubble (under the name stage name RyuA) and on March 22, debuted in the group with their first digital single “Popcorn”, shortly after that she left the group for unspecified reasons.
On July 10, 2018, she was revealed to be a member of SATURDAY and officially debuted with them on July 18, with the digital single “MMook JJi BBa”.
Source: kpop wiki