
..that ML is not human. Maybe he is death. One of Sisyphus's sins was that he captured death and people could not die (so sick and very old people were tortured by this) and the Gods restored the natural order. Sonic Death lost his powers and memory and roams the earth as a human, people do not die.
But another theory of him being patient zero, an experiment maybe similar to Frankstein's monster that have an allergic reaction to human DNA, and due to his existence the zombie virus was created and spreaded is also a possibility
..Because the Au story was actually the real story and the FU story was a script. Creators have the right to create whatever they want (fluffy, dark, anguish, whatever) same as we have the right to like it or not. But I like the hinted note in the end of the optimistic pure love being the real one, while the other is a movie