The game's premise is extremely unnerving, even by today's standards. The gist of it is that you, Simon Belmont, sustained some nasty injuries while fighting Dracula that one time. They're not healing, you feel lousy, and then one morning this guardian spirit appears to you! And she says 'Dracula cursed your wounds, and if you don't exorcise his ghost post-haste, you're going to die and he's going to use your body as his next vessel.' But just keep telling yourself, it's only a video game.
The Japanese manual is even worse — Simon's not just got unhealing nasty injuries, his body is starting to decay like an aged corpse's. And the guardian spirit cautions you that the exorcism ritual might not work.
Carmilla, in her first appearance, is a giant, grinning, disembodied mask that hovers about and weeps flaming tears from one eye, like an even creepier version of Phanto.
In the five mansions, you can find corpses hanging from the ceiling, which is unsettling even with the 8-bit graphics.
The towns are lively and filled with human activity during the day, and when night falls, all the stores close and now there's an indefinite wave of undead out for your blood in the once-safe village. "What a horrible night to have a curse" indeed. The last few towns have increasingly unsettling dialogue, going from people scared they're going to die to a town where everyone is terrified of Simon and demands he leave, to the final town nearest Castlevania which is almost completely barren save for one NPC that requests, "LET'S LIVE HERE TOGETHER." Why? Who knows.
