Lumaking7@ I believe I got a story idea of Yugioh Zexal about Zaira's disappearance. Somehow, Zaira left Barian World by choice because she was feeling miserable, guilty, and desperate.
Miserable for having feelings not just for Dumon but to Nash as well, so he somehow rejected her extremely hard, which broken her heart. Guilty for not telling Dumon and everyone else, including Vector, for falling in love with Nash, knowing her brother holds a grudge against him.
So she desperately made a deal with Don Thousand to erase her emotions, her love towards Dumon and Nash to fulfill her duty as a Barian Emperor even if it means going to Astral World. What do you think? I hope this story idea of Zaira is helpful