Kingdom Hearts 4: Who is the Nameless Star?

gamerant.com:

There are many outstanding mysteries in the Kingdom Hearts franchise. As its story uses a compounding narrative approach, every entry contributes something to the series’ overarching lore. This has irritated its fair share of fans and contributes to new players struggling to penetrate later games. Still, when someone recognizes a detail brought up in a later Kingdom Hearts title as something from an earlier one, there is a sense of pride in keeping up with the full picture that is Kingdom Hearts. Kingdom Hearts 3 and Kingdom Hearts Union Cross in particular have left many threads dangling for Kingdom Hearts 4 and other games to pick up.

One of the most detailed mysteries so far is the Nameless Star found in Kingdom Hearts 3’s Final World. Sora, and later Kairi and Riku in Melody of Memory, stumble across this soul clinging on to existence. She tells the heroes what she knows about Quadratum, and asks Sora to help Yozora — whose heart is said to not be his own. The Nameless Star cannot help any further, as her heart and identity have been stolen. Kingdom Hearts 4 is expected to divulge more on this enigma, but according to series director Tetsuya Nomura, fans have already met the Nameless Star in another life.

Kingdom Hearts 4: 9 Lingering Questions The Game Could Answer

Previously, a common guess for the Nameless Star's identity was the dead Strelitzia from Kingdom Hearts Union Cross. That theory has since been shot down by her appearance in the Kingdom Hearts 4 reveal trailer. All that fans know about the Nameless Star is that they knew Yozora, are from Quadratum, and the Star is an existing Kingdom Hearts character. Its most likely identity is the girl seen in the Verum Rex game trailer at the start of KH3’s Toy Story