Taking place after the end of the war over Newtypes and D.O.M.E. in After War Gundam X, Under The Moonlight tells a new story of a boy, Rick Aller who finds a still-useable Gundam X, and his adventures while tracking down an AWOL friend, Kai, possessing the Gundam Belphagor.

Taking place after the end of the war over Newtypes and D.O.M.E. in After War Gundam X, Under The Moonlight tells a new story of a boy, Rick Aller who finds a still-useable Gundam X, and his adventures while tracking down an AWOL friend, Kai, possessing the Gundam Belphagor.