Once a promising child soldier in the service of the Vodka Kingdom decades ago, Kaidou was drafted against his will by the Marines but managed to escape and start a career in piracy. He was invited by Edward Newgate to join the legendary Rocks Pirates as an apprentice, where he met and befriended Charlotte Linlin. During the God Valley Incident when the Rocks Pirates met their downfall, Linlin provided Kaidou with the rare Mythical Zoan-type Devil Fruit, the Uo Uo no Mi, Model: Seiryu.