ML is essentially the world's creator + is later a member of a criminal organization
MC is a famous assassin
MC is not a human child but an android
MC is a vampire
MC is Arachne
As the title says... there are A LOT of things she's hiding about her identity:
1) she's a girl, not a boy
2) she's a runaway mage
3) she's a child soldier
And a lot of other stuff
MC is a dragon
MC is a villain
MC is the empire's strongest knight, not a common maid
Winterbell