It’s not clear when Lumina first appears in Nova Chrysalia, but she was not there from its beginning.

To a world with an undying population, she is an oddity. She is new, and most of the population know of her because Lumina makes a name for herself. Enigmatic as she is mysterious, Lumina’s goals are her own; she’s a mischief maker and does what she pleases, when she pleases. She’s whimsical and brattish, and ultimately, selfish. Yet, what she wants most is to be loved. She calls Lightning her sister, but clearly isn’t. Or is she?

Lumina is, first and foremost, a cornerstone of unwanted behaviours, specifically Lightning’s. She eventually reveals herself as such - that she’s Claire Farron, the part of her soul that she couldn’t accept. The part of herself she felt she had to sacrifice in order to be strong for Serah after their parents died. Sure, she’s an exaggeration of selfishness and fear, because that’s what she’s made of, a lonely child that was abandoned so as to be replaced by the strong, stoic young woman that would become Lightning.

But does she look like Lightning?

Lightning doesn’t think so. She thinks she looks like Serah at the age Lumina is presented. Still, Lumina might have looked more like Lightning at that age, and in this respect, Lightning is an unreliable narrator - she would never associate herself in such a way, regardless of how many years she’s lived. Never forget that Lumina is a cast-off, in all facets. Then again, Lightning and Serah are sisters; it’s natural they would look alike as kids, so resembling the both of them is not illogical if she is sourced from Lightning.

Yet, whilst Lumina was made from Lightning’s emotions, she was made from Serah’s soul. That also counts. Lumina is a vessel, a tomb, fashioned specifically to contain Serah’s soul; Bhunivelze never has ownership of Serah, because she is Lumina.

Here’s the trickier part. Whilst Lumina’s behaviour is erratic, she is capable of random acts of kindness. Her help might be unconventional, but it will be attempted - the citizens of Nova Chrysalia see it as well meant. She watches over Lightning’s friends before she wakes, too, checking in on them to see how they’re getting along, dropping hints…

This cannot be Lightning. Lumina is a Lightning that cared only for Serah, only about herself, at a point in her life where she prioritised Serah over everything else. A Lightning that is still prepared to watch over her younger sister… except this time, it’s the part of herself she assumed would not be able to do so that fulfills this duty. So, where did Lumina’s capacity to care and reach out to others come from?

This has to be Serah. Serah’s friends are the same as her sisters, so is it her soul, reaching out to them, haunting them, trying to tell them that she isn’t really gone? The soul, the heart of a person, is the same, even if the vessel is slightly different. Every Yeul is different, but they share a soul, the same kind of person, born over and over again. If anyone would have a “rebirth” of a sort, wouldn’t it be the other canonical seeress? Perhaps Lumina inherits Serah’s memories, and that’s why she knows so much. Perhaps that’s why she’s not entirely a malicious entity. Perhaps that’s why her magic stems from the same part of her body where Serah was branded a l’Cie. It’s certainly why she calls Lightning “sis”. There’s a lot of unanswered questions when it comes to Lumina.

Ultimately, is Lumina Lightning, or is she Serah?

Neither. She’s both.