둘도 없는 그런 사이, 우린 진짜 특별한 사이. 그런 친구사이, Best Friend. Lyrics by SUMIN, 우원재 Composed by SUMIN, 우원재 Arranged by SUMIN Drums Performed by SUMIN Bass Performed by SUMIN Keyboards Performed by SUMIN Synthesizers Performed by SUMIN Background Vocals by SUMIN, 우원재 Mixed by SUMIN Mastered by Nahzam Sue (@Wormwood Hill Studio) Artwork by Soyo