Soshite Kimi wa Tsuki ni Natta
English title: And Then You Became the Moon
Japanese title: そして君は月になった
Type: Music
Episodes: 1
Source: Original
Duration: 4 min
Rating: G - All Ages

This song is about two best friends that are represented as the moon and the star. The song seems to be expressing a close friendship that also develops distance gradually.

(Source: Vocaloid Wiki)