Mario and Luigi are at the beach buying 500 hot dogs, so Mario can break his eating record. While his brother is eating, Luigi gets wind of Saiko (Fishy Boopkins' former girlfriend from Doki Doki Mario Club who broke up with her due to her psychotic nature) sitting next to them, and freaks out after she makes a sarcastic "Boo"(showcasing Luigi's cowardice). However, Saiko tells the green plumber she doesn't want to hurt him and orders him to leave her alone, but Luigi tries to cheer her up with one of Mario's hot dogs, only for her to refuse, causing him to throw the hot dog back to Mario.
Luigi then walks up to her and reminds her of how every time she gets upset, she goes insane and tries to kill them for no reason at all, and how she's acting different, so he offers to rehabilitate her by teaching her the meaning of good manners. Unfortunately, Saiko fails in every assignment Luigi gives her, much to her annoyance so she decides to quit, much to Luigi's depression.
Meanwhile, Mario has finished eating all 500 hot dogs without fattening up. However, the second he starts celebrating, he gets a heart attack. Luigi starts panicking, repeatedly asking for help, but no one comes. Finally, Saiko shows up to help him, so they get on a motorcycle and drive Mario to the hospital, and despite all the traffic, they manage to do so by throwing Mario's nearly dead corpse into the window. Luigi quickly thanks Saiko for saving Mario's life. Saiko gives Luigi a smile before taking off.
Afterwards, Mario comes out of the hospital completely fine after his near-death experience, and quickly gets hungry, so he decides to eat more hot dogs, much to Luigi's dismay.