The Ex-Hero Is Too Good at Exorcism

Reader says:

The story starts long after the MC has returned from the other world after dying and failing as a hero. After returning to Earth without any of his powers, the MC finds that little to no time has passed since he was sent to the other world. He tries to tell his story of the other world, but no one believes him.

Now sometime later, after he has settled down, the story starts. He eventually gets tangled with spirits and exorcists and becomes an exorcist. The abilities of an exorcist are somewhat similar to the abilities he had in the other world, but ultimately they are different as they use spiritual power as there is no mana or aura on Earth. This is also the reason why the MC hasn’t bothered to try and train himself as there is no mana or aura to use, meaning that even if he trained he would still just lose to a gun. Now an exorcist, the MC uses his experience as a hero to grow stronger, along with his new supernatural ability, the system(this is not sarcasm, his unique supernatural ability is literally the system).

The rest of the story I assume would be about the MC growing stronger as an exorcist and his experiences.