Sure, you have read lots of stories where the main character has a system, but how about one where he is the system.

This story follows john, who dies and gets reincarnated into a fantasy world as a... system? How will John continue his daily life when he is a system? a being of near omnipotent power. This story will follow the protagonist as he fulfils his duties as a system and how he spends his life watching and messing with the inhabitants of the world he now oversees.