Tekkadon

Rinse Japanese short-grain rice thoroughly under cold running water until the water runs clear. Drain the Japanese short-grain rice and place it in a rice cooker with Water. Cook the Japanese short-grain rice according to the rice cooker instructions.

While the Japanese short-grain rice cooks, prepare the sushi vinegar by combining Rice vinegar, Sugar, and Salt in a small saucepan. Heat gently over low heat, stirring until Sugar and Salt are fully dissolved. Do not boil. Remove from heat and let the sushi vinegar cool completely.

Prepare the tuna marinade: In a separate small saucepan, combine Soy sauce (koikuchi), Mirin, and Sake. Bring to a gentle simmer over medium heat for 1 minute to cook off the alcohol. Remove from heat and let the marinade cool completely.