Basically, Issei is the reincarnation of Xehanorth and Eraqus. After Xehanorth was defeated by Sora he was rejoin with his best friend Eraqus, but still was worried about Sora, and new threats coming his way. So, he decided to stay back to get reincarnated. Asking if Eraqus wanted to come along with him, they fuse into a new being becoming Issei Hyoudou. Before anyone asked how is that possible, please watch the ending of kingdom hearts union cross to understand were keyblade wielder's goes when they die. They have an option to sleep, or get reincarnated Summary will be updated in the future! Sora, Riku, Kairi and the rest of the kingdom hearts gang will be in their early thirties because 16 years have passed. Storyteller
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