In a rice cooker, combine sushi rice and water. Cook according to the rice cooker instructions.

Once cooked, let the rice cool slightly, then mix in rice vinegar, sugar, and salt. Spread the rice onto a baking sheet to cool completely.

Heat vegetable oil in a frying pan over medium heat.

Once hot, form the cooled rice into small squares and fry until golden brown and crispy on both sides. Drain on paper towels.

In a mixing bowl, combine diced tuna, mayonnaise, sriracha, soy sauce, sesame oil, and chopped green onions. Mix well.

Top each crispy rice square with a generous spoonful of the spicy tuna mixture.

Garnish with black sesame seeds and microgreens before serving.