i Register
In some senses, grimdark is marked as slang. Watch for register when choosing this word.
adj
Of a film, television programme, video game, written work, etc.: having a gloomy, dystopian atmosphere.
If your character is a more-or-less ordinary little girl fighting for her life as a usual thing, that's a fairly GRIMDARK setting; it implies that there isn't any Good authority with both the power and the will to protect them.
Most original. Brilliantly so! What's not to like? "Jarringly non-grimdark," carpers will sneer. Oh, yeah? What's not Grimdark about – / * Droids? / * Vagina heads? / * Gundam suits (desu)?
noun
The literary genre of speculative fiction that is amoral, dystopian, or violent.