CompletedNichirin Shinichi transmigrates into a world where he becomes bound to a "Persona System."
The system offers him a variety of personas to choose from, including deity personas, sword-wielding personas, exorcist personas, and demon-slaying personas, all meant to maintain world peace.
Looking at the state of the world—Yokohama constantly being demolished by literary heroes, Tokyo threatened by falling swords, Kyoto bracing for a hundred-demon night parade, and the death god detective permanently stationed in Beika Town—Nichirin decides it's time to take action.
The cities themselves start to manifest consciousness to protect their own integrity:
"The city has a personality!"
"At least Yokohama is a proper lady...right?"
"A lady who smiles while dismantling white whales?"
"Kyoto is a drunk aristocrat who calls herself Chang'an after too much sake and runs trains through the night!"
As cities awaken and begin purging "pests" themselves, true peace finally arrives in the world.