Secretary of the Devil's Castle

Fatalia is a time traveler, a young white-haired succubus, a poor child who fell into the wilderness for some reason, and still has a waste system in her mind that can only look at the panel.
But one day, she managed to unearth another use for this waste system.
Facing the abyss where you can get rewards at a price, she said: "I want to sacrifice the system."
She succeeded.
(This is a serious story about a succubus assisting the devil to plan to overturn the whole world)
(emphasis because the label is gone, it is orange)
(Reminder in the front row, the protagonist will grow up, you can refer to the cover for the mature image, not always a loli)