I'm thinking the latter.
World of Supernatural that just got hit by an apocalypse which is why the supernatural world is mingling with it.
I'm thinking a kid with a small interest in the occult buys a book that he doesn't believe works, opens it and unleashes the terror upon the world, causing everyone around him to die - make him some bookworm type character that only knows how to survive because of zombie games. Visa versa, I'll play another character who is a bit of a snobby rich kid who can't live without his electronics, and the two end up meeting through the issues, they build a friendship and 'may' end up together, who knows.
Alternatively we have two supernatural creatures, maybe a werewolf and a vampire (hell, could even have plenty more characters to throw into the mix anything supernatural, minx, elves, fae, demons, ect.) Possibly have these two either match up against the two 'human' survivors, or even with eachother ^^
Throw in other characters here and there and see which ones to drop and which ones to keep ^^
-- and yes, I did just come up with this idea off the top of my head.
