Looking at Loki and Gunko/Shuri, it is clear they are meant to be opposite sides of the same coin. Born into royalty with special eyes who would eventually commit regicide/patricide (Loki obviously did not do so voluntary, and it is very likely the same case for Shuri too). However, Shuri was elevated because of her eyes, while Loki would always be considered an accursed prince.
Loki got his size and horns from his father, Harald, and I believe he got his eyes from his mother, Estrid. Obviously both parents have ancient giant blood, so Loki could have gotten them from Harald, but Hajrudin does not have those eyes. Now Hajrudin takes more after his mother, Ida, so why can’t Loki be the same with Estrid? I think deep down Estrid knows those eyes she hates came from her, and that thought is so repulsive to her It causes her mental breakdown and eventual death.
My Theory is this: Shuri got her eyes from her mother, Candelle. I think Candelle is connected to the CD’s, maybe a Bonny type reject, and that is how Shuri is a Manmayer. Estrid is described as carrying “noble blood”, so maybe Candelle carried (world) noble blood too?
Gurou said being born with Heterochromia is very rare, so there are most likely Manmayer’s without it. Shuri also never directly calls Gurou her father, or Gurou calls Shuri his daughter, she just says her “family” is Celestial Dragons. I am not sure why Candelle was bedridden, or what Shuri was talking about when she said Reuven was not her ”real” father (she was also literally possessed by a demon, so maybe take it with a grain of salt, or at least deliberately hiding context).
I know this situation seems like a Ginny/Bonny/Kuma type deal, but there are so may parallels Shuri shares with Loki that it would not surprise me if they share a similar bloodline origin as well.
My Theory is this: Shuri got her eyes from her mother, Candelle.
This has been deconfirmed. Shuri got them from her father, Gurou, who is a Manmayer and confirmed to be Shuri's biological father. The implication is that Candelle became bedridden due to her pregnancy, due to the timing of her meeting Gurou and Shuri's birth.
I think this started well by kinda took a left turn. Gunko obviously got it from her father who has the same eyes. He also said awakening the ability was rare not the eyes. When it comes to Loki, you cant really say Harald isnt is his farher bc Loki is an amcient giant and his mother is also obviously the one rhat carried him. I think a more likely theory is that she might have been influenced qhile she was pregnant by some ritual maybe