An interesting fact about these ethnical Koreans commonly referred to as Zainichi(在日 literally means residing in Japan in both JP and chinese) Koreans is that they are divided in two categories those who own their allegiance to North Korea and those who hold it to the South, there is even North Korean schools in Japanese soil where they have portraits of NK leader and profess to follow their ideology something which I believe is still illegal in South Korea and would get you arrested.
But in recent decades more and more of these people are choosing to naturalize as Japanese and many can't speak Korean at all
Aespa Giselle already revealed that she is half-half. She was born in Seoul to a Korean mother but her father is Japanese, so unlike Yoshi (who was born in Japan but wasn't given citizenship there) she had dual citizenship when she was little but she chose Japanese citizenship when she came of age, so now she is just a foreigner in Korea.
I see now that she confirmed being born in Seoul in the same Youtube series from the OP. Interesting so she moved to Japan sometime after being born, do you know if her father is a naturalized former Zainichi or ethnical Japanese?
This is the information that we've been told so far, by people who knew her etc. so I'm just going along with that. Unless she states otherwise, this is what I'll assume, but that will make no difference to me either way.
It seems she is confirmed to have inherited both nationalities from each side of her parents but choose to keep her Japanese nationality