Lyrically it deals with the group saying "sorry" towards each other, using the Japanese word "Gomennasai"; hence the title. "Gomenasai" received mixed to favorable reviews from music critics, who felt it was gentle and one of the group's best vocal songs to date, while some felt it was similar to other ballads.
Lyrically, the song centers on apologies between members of the group using the Japanese word "Gomennasai," which is reflected in the title. Music critics had mixed opinions about the song's quality, with some finding it a strong vocal track and others feeling it was similar to other ballads.