Ray is the incarnation of Yuzu Hiragi (Standard Dimension), Serena (Fusion Dimension), Rin (Synchro Dimension) and Ruri Kurosaki (Xyz Dimension). She is Leo Akaba's daughter and a pro-duelist in the Original Dimension. In her father's place, Ray confronted Zarc, which resulted in her soul being split into four and reincarnated into four different lives. She is a key part to his plan, Revival Zero.
(Source: Yu-Gi-Oh! Arc-V Wikia)