While that already most plausible theory has become still more plausible, it is not yet confirmed. For example, what if Mishou (Mute) was to be a humanoid sister to Suoh, but Mishou had to have her organ of thought put into a different body from what was planned? It's a stretch, but not completely ruled-out.this chapter reaIIy confirmed that; mute is the master she Iooking for IoI finaIIy
Consider, for example, a theory that Suoh is occupying a body originally intended for Mishou. Perhaps Suoh was not supposed to be as sentient as she was, or perhaps Mishou had originally disregarded that sentience, but then realized that she were dealing with a person, whom she could not rob of the body that she'd been given.Some experiment or accident must have happened that Suoh is unaware of, and they probably don't want to burden her with the details