YOS is the first sub-unit from Apink consist of three members: Bomi, Naeun and Hayoung. The group "officially" formed in 2018 as an April Fool's joke.  No song was released back then. They made their first variety show appearance on Idol Room together with the rest of the Apink members. After almost two years, the group released a song called "Love is Blind" which is included in their 9th mini album "Look".