I think elijah or avery is a noble's daughter. But due to some circumstances she is hidden...

I was thinking the same

SPOILER
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I read on a forum that she is a noble's daughter, the redhaired woman that appeared at the end of ch 37 is her aunt or something, as You can imagine she's the cause that she has to dress like a boy, there's something with the succession of the family and the aunt wants to take over the family, and Avery is a threat for her plans, so she will try to get rid of her

Ooh so what i thought is actually accurate... tnks for the spoiler