- Zero is Xion, or what is left of his soul. His angelic wings represent the two entities inside his body, the black one resembles Zeroboros , the white one resembles what is left of Xion. It seems he went to Elde to find someone able to replace him as Guardian of End Earth. He chooses Souma, and after meeting him between worlds, states that he now 'entrusts' the world to him. He gave Souma one of the Twin Dragon Rings, telling him to use it to see the true world.
- He keeps running from Mao, as some time before, he unwillingly killed Ryuna and Lazarus. It was Mao's calling that made him fight Zeroboros' possession, turning one of the black wings white, thus leaving a piece of Xion's soul. He accepted himself as no longer human, and revived Ryuna and Lazarus using the capsules in the Sea Dragon King Ruins.
- He decides to leave the group and entrust Souma with protecting the world in his place
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