This is great. I want to post a recap.
Mario and Co. are walking through Sayonara, when suddenly...
the Ninjis! And Karate Koopa but no CatDog. We start off by Mario going in front of a Ninji and being thrown. Then Luigi get surrounded by two of them and one of them kicks him and he lands in a pile of trash. Koopa then orders his Ninjis to tie up Princess and Toad. A Ninji spins Princess around. Another one is holding a rope. He throws it at Princess, tying her up. Toad is surrounded by them and he gets spun around and tied up. The Ninjis bring Toad to Princess and we see Mario dizzy and Luigi as his alter-ego, Trash Head.
MISAKI!!! He destroys Ninjis. Meanwhile, Koopa throws Toad into a wheel thing and orders his Ninjis to throw Princess in. They do so. Misaki destroys more Ninjis. He throws one very far.
The Marios are now at Misaki's dojo. Misaki chops a brick. Mario asks "When's lunch? I'm starved!". Misaki throws Mario across the room. Misaki hands Mario a stick. Misaki grabs it, and he throws Mario across the room (again). They go outside and the Marios learn Plumb Fu.
Cut to Koopa's dojo. Princess and Toad are tied to a pillar. Toad says something. Notice that he isn't where he's supposed to be! Koopa taps his head and pulls out a pair of binoculars. He sees the Marios and Misaki walking to Koopa's dojo. He then throws a net above them. They are now chained to a boulder on a catapult. Koopa pulls the catapult, throwing them into the ocean. Mario cuts the chain and they fight a horde of Trouters. They go inside Koopa's dojo and fight Ninjis.
Cut to Koopa's room. Koopa says that the bidding for Princess and Toad will begin in a few minutes. Koopa drinks some Koopa Kola. Princess and Toad are trying to untie themselves. Princess unties herself and Toad. They run off. Koopa grabs them and Mario hears Princess scream help. Mario fights Koopa and wins, but Koopa gets away into a warp zone. Mario and Luigi are awarded black belts.
So there are 2 plots.
Plot: The Marios and Misaki go defeat Koopa.
Subplot: Princess and Toad try to untie themselves.