24 years ago.

Near the mushroom kingdom there is a Kingdom called the Dark Lands which is ruled by the Koopa Royal family which is made out of 70 members.

But one stormy day almost the entire family was slaughtered by Union for they see them as monsters yet what they don't know is that the youngest and heir to the Dark Lands is Y/N Great Demon Koopa nickname Bowser who glare at Union as they leave.

Young Y/N: "I swear on the name of Koopas that you false heroes will pay" he said as his hair catch on fire.

Present day.

At the Mushroom Kingdom the civilians are celebrating the 25 anniversary of Union killing the Koopa monsters however Princess Peach sigh with sadness as she misses her friend Y/N Koopa.

When the skies turn dark and stormy surprising everyone but then the civilians panic as a castle exits the clouds.

Before Union could attack magic froze them in place then the castle landed in front of the Mushroom kingdom then thousands of Koopas ran out of the castle.

Then everyone heard big thumps coming out of the castle then to Union shock and many civilian horrors exiting the castle is a Royal Koopa.

However Princess Peach is speechless as she knows who's that Royal Koopa is.

Peach: "Y/N?" She said with a blush.

Bowser: "So Union you thought you got rid of the Royal Koopas? Well sorry to disappoint you all but I am the last of the royal Koopas and I am King Bowser!" He said then unleash a powerful fire blast that completely destroyed an Atlas ship.

Ironwood: "You vile monsters deserve death!" He said only to scream as he got burned by Bowser yet he survived but only barely.

Bowser: "And slaughtering my family especially the young makes you heroes?! No you are killers who believe they are heroic when in reality you're fakes" he said then Issei broke out of the magic and attempted to punch him.

Yet Bowser grabbed his arm and to Union shock Issei's dragon arm vanished.

Issei: "What did you do to ddraig!" He said.

Bowser: "Simple. He is free from your perverted body" he said then he unleashed a fire blast that completely vaporized Issei completely horrified Union.

Rias: "You monster! You pay for killing my beloved Issei!" She said then broke out of the magic and threw a ball of destruction at him yet he grabs it then easily devours it.

Bowser: "Thanks for the new flames sl_t" he said then fired a new flame ball that completely vaporized an incoming Atlas fleet.

Ozpin: "He's too powerful" he thought then Sirzech broke out of the magic then teleported Union away.

Bowser: "Pathetic. Koopas army! Return to the castle" he said which his soldiers salute then walk towards the koopa castle.

Then Bowser looked at Peach who is now standing in front of him.

Peach: "Y/N" she said with tears running down her cheeks while Bowser sigh.

Bowser: "Yeah Peaches" he said then Peach hugged him.