Y/n L/n is the son of Mario and the nephew of Luigi and the three of them go on countless adventures together in the Mushroom Kingdom. Until one day when Luigi betrayed both his brother and nephew and worked with Bowser to get revenge on them after getting tired of living under Mario's shadow for too long.

However, when Luigi had the upper hand of killing his own brother, Y/n made an attempt to stop him but resulted in him falling into a pool of molten lava, killing him in the process

Luigi was both shocked and heartbroken to see his own nephew die in the lava pit and soon regretted and blamed himself for his actions.

Eventually, Luigi went under a deep state of depression and regret as he tried to move on with his life and forget what happened on the day of Y/n's death, despite of his brother Mario and the others shunned him for what he did when he still worked for Bowser before Y/n died in that pit of lava.

Then one day, when he went exploring through World 1-1, he soon heard a familiar voice calling to him and found his nephew alive and well, but didn't realize that Y/n came back from the dead to get revenge on Luigi for his actions as he sent Luigi to his own world, where he will faces many dangers that Y/n aka Mr. Anon has created to give his uncle the eternal punishment of his life as payback for killing him and betraying the family for his own jealousy and hatred towards his brother.

How will the green plumber survive and escape his own nightmare, controlled by his own nephew aka Mr. Anon?