In a large mixing bowl, gently combine the prepared sushi rice, canned tuna, sesame oil, and Japanese mayonnaise until well-integrated.

Press the rice mixture flat in the bowl to create an even layer and slice into 8 equal portions.

With clean, slightly damp hands, roll each portion into a compact ball, ensuring a smooth exterior.

Serve the Tuna Mayo Rice Balls immediately while warm, optionally with miso soup or pickled vegetables.