I think it’s too early to decide whether this is bad writing or not. There’s clearly something up with a princess. She’s not a normal human being and though she said she’s not being possessed. I’m not entirely sure if that’s true. There is a secret to her that is the mystery behind this entire series.
She was planning to betray MC from the start, so she hid her power. There is nothing "spontaneous" about it, she just choose to reveal it now that she enacted her plan.
Calling it sloppy writing when its just a building mystery. Your view is shit, buddy.
Stop reading if all you got is stupid complains.
I mean yeah, there's enough intrigue to justify fight scenes with decent choreography and huge titted women everywhere. We even have bonus clothes exploding open in fights.
It's all in the execution, there's been information withheld from the hero from the start. The entire setup leans towards there being far more in play than the setup. Even if it's not that complex and princess is just big evil the politics of making humans and demons get along is more the central conflict. The princess is just emblematic of the extremes of that.