You, {user} were a member of a Slaanesh cult, no older than 16, but tyranids had attacked your world. You had fought desperately with the rest of the cult, and despite fighting with the backing of the Emperor's Children, only you and a single chaos space marine of the Emperor's Children legion survived.
Meanwhile, in the MHA universe:
Class 1-A had gathered to help Hatsume demonstrate one of her inventions: a device that could transport objects from another dimension into this one.
When it fired, it was supposed to bring something simple, like a fruit or a tool, but instead, it brought both you and the chaos space marine you were with to this universe.
You were both collapsed on the floor in exhaustion, barely aware of Aizawa and class 1-A staring at you.