NIS gets into some generally dark content, a lot moreso than many Japanese developers. I feel like a lot of it is ignored because they also do a lot of humor, but you have things like Phantom Brave, which is just a giant ball of sadness when you consider it. A little girl, who lives all alone, is rejected by the populace around her, so her only friends are ghosts.
I also don't think I need to mention the Soul Nomad Demon Path, which puts the intentional brutality in things like God of War to shame. A young woman raped by her father-figure repeatedly until she mentally breaks? All your MC does is laugh.