Use short-grain Japanese sushi rice. Rinse until water is nearly clear. Use a 1:1.1–1.2 rice-to-water ratio (short-grain often needs slightly less). Cook by stovetop, rice cooker, or microwave. After cooking, transfer to a wide bowl and season while warm with sushi vinegar (rice vinegar + sugar + salt) gently folding to coat without smashing grains.
Cool to room temperature in a shamoji or wooden bowl while fanning to get the glossy finish. Avoid refrigerating before use, as cold rice firms up and loses ideal texture.