"Farewell Song" is an original work by Shinjou-P featuring KAITO. It is a light-paced song with strong harmonies of piano and violin. The lyrics can be interpreted as a farewell song to a lost lover and the yearning for those days of love. The "na 4M" line in the lyrics comes from Vocaloid phonetics. This song has entered the Hall of Fame. It is featured in Shinjou-P's album The First Unison.