"Happy Days" is Ai Otsuka's fourth single.

The title track was used as background music in the Morinaga ICE BOX CM, which starred Otsuka, and as the theme of Koukousei Quiz 2004 on Nihon TV.

It also contained a new b-side song "Hoshikuzu" (星くず) and instrumental versions of both songs.

All tracks are written by Ai OtsukaTotal estimate: 163,433

This 2000s Japanese single–related article is a stub.