Cook sushi rice according to package instructions.
In a microwave-safe bowl, combine rice vinegar and sugar. Microwave for about 30 seconds, or until the sugar dissolves.
Pour vinegar mixture into the cooked sushi rice and gently mix until combined.
Prepare Shrimp Mixture
In a bowl, combine chopped shrimp, light soy sauce, Kewpie mayo, sriracha, and sesame oil. Mix until the shrimp is evenly coated.
Assemble the Sushi Cups
Preheat oven to 400°F. Lightly grease the muffin tin with cooking spray.
Cut each nori sheet into four squares or rectangles large enough to fit inside your muffin tin cavities.
Place one piece of nori into each muffin tin cavity. Add a spoonful of seasoned sushi rice and gently press it down. Top with a spoonful of the spicy shrimp mixture.
Bake the Sushi Cups
Bake at 400°F for about 15 minutes, or until the shrimp is opaque and cooked through (145°F internal temperature).
Let the sushi cups cool for a few minutes before removing them from the muffin tin. Drizzle with extra sriracha or spicy mayo, then garnish with sesame seeds and chopped green onions. Serve warm and enjoy!