Ok, it turns out you need a genuine, retail cart in your slot 1 in order for this game to work. The reason? It saves directly to your slot 1 cart! I lost my castlevaniaOR saves because of this stupid game, so don't bother unless you have a retail cart with saves you don't need.
Maaaan I was close to finishing my Richter file on hard mode - if I wasn't so lazy to actually beat it, I' be pissed. Now I have 2 brand games