It's also used as a B-side for B1A4's second Japanese single, Oyasumi Goodnight.
So Fine was written by Baro and 우리형과 내동생 (My Brother and My Sister). Composition was done by My Brother and My Sister along with Ichiro Suezawa.
MEG.ME translated the Korean lyrics into Japanese for the Japanese release of the song.
The song was promoted through B1A4's first solo tour, BABA B1A4 In Seoul.
Additionally, CNU performed it as a solo song in their second solo tour, Amazing Store.
See So Fine Lyrics