Fan Service [sweet] was the group's first single for the year 2007.

The release date coincided with Valentine's Day, a theme present in the song "Chocolate Disco".

It was issued in special packaging containing a DVD with music videos and a 20-page booklet, and only a limited number of pressings were produced.

Both songs were included in the group's album GAME, released the next year.

"Chocolate Disco" has been referred to by young people as a "traditional Valentine's Day song".