There was a news that new member, Yeri would be joined in girl group Red Velvet.
Related to this, an opinion saying that the group was member rotation group
from the first time became hot in Korea's online community.

Netizens who saw the debut song 'Happiness' Music Vedio
and portal search result picture had reactions like,
"Its weird that her name is in the trainee group member list even though she had an official debut,"
"Then will the boy group who has a debut this year from the Rookies be a member rotation group?,"
"I liked Red Velvet with 4 members...," and "SM manager! We don't need things like member replacement!"