Monika's whole deal is being self-aware of her code while existing in a story about love. The tension explodes from that gap. She knows the player, the MC, isn't real in her world, but her feelings are. So fanfics I've seen dive into the horror and tragedy of that. She might manipulate the game's code, literally rewrite a scene to force a moment, only to stare at the results and realize it's hollow because she scripted it. The drama isn't just "will they, won't they." It's "can they, when one of them is a collection of pixels and the other is a player behind a screen?" The best ones make you feel her desperation—her love is real, but its object is an ontological impossibility.
Some writers flip it, making the MC somehow aware of her actions, which creates this paranoid, cat-and-mouse dynamic. He might find traces of deleted characters in the game files, hear glitched dialogue. The tension becomes a psychological thriller. Is she a monster for deleting her friends for him, or a victim of her own programming? That moral gray area fuels incredible drama, way beyond typical romance stakes. I'm always drawn to fics that don't shy away from the bleakness; a happy ending for them has to be earned through some serious metaphysical problem-solving, or it just rings false.