Japanese rice (or japonica) is a short-grain rice which is characterized by its unique stickiness and texture.
You might see the name “sushi rice” on some of rice packages, however that is just a product name referring Japanese style rice. The Japanese only call rice sushi rice when we are referring to sumeshi (vinegared rice) to make sushi and we do not eat sushi rice for regular meals.
I often receive questions about which brand of rice I buy.
I get this brand of Koshihikari from a local Japanese grocery store. Some Asian grocery stores carry this brand too.
Substitution: According to wiki, Italian short grain rice, arborio rice, is considered good substitute. The long-grain Jasmine or basmati rices will not go well with Japanese meals. I buy California grown Koshihikari (コシヒカリ) or Tamanishiki (玉錦) at Japanese supermarket.