The Super Bros' Sister (Bowser x Sister! OC)

Marzia is Mario and Luigi's younger sister. She has a Lady-like personality but isn't afraid of getting her hands dirty.

While working underground to fix a water main, Brooklyn plumbers and brothers as well their well-mannered but sassy sister: Mario, Luigi and Marzia are transported through a mysterious pipe to a magical new world. But when the siblings are separated, an epic adventure begins.

However, what happens if Marzia encounters an evil Koopa king himself, Bowser? Well, that wasn't part of the plan. At least, she knows how to tame the beast.