Responses
Imagine you transmigrated holding this rule but the heroine of your world is actually pure and kind hearted and you ended up being the delusional villainess. ToT. I mean no ill will but just imagine the chaos.
That's okay, she can be pure and kind-hearted or be a manipulating and conniving lunatic, being guarded is always good, goodwill can be a manipulation to someone who doesn't want it...
The first cardinal rule of being isekai-ed is never hold any good will towards the FL, just believe she's a manipulating, scheming lunatic