Rinse sushi rice under cold water until it runs clear and cook according to package instructions, about 18-20 minutes.

Combine rice vinegar, sugar, and salt in a separate bowl, dissolving completely.

Fold the seasoning into the cooled sushi rice gently.

Finely dice fresh ahi tuna and mix with sriracha and mayonnaise.

Wet hands, take a handful of sushi rice, and form a triangle with a small indentation for filling.

Spoon tuna filling into the rice indentation and mold the rice around it.

Wrap nori around the onigiri and serve.