waa I still have to work on Zukii's backstory
BUT the main reason was when Zekki met Zukii, he altered the timeline, resulting in a paradox
because time crystals are unstable in the future, Zekki trusted the crystals to Zukii as a way to evade his fate, and created a time rift where both of them were trapped
then Zukii became like the personification of the paradox(? because of this reason
yeahhh,, time paradox stuff I guess xD