Kokumotsu Su (穀物酢), or Japanese grain vinegar, is a mild and versatile vinegar brewed from a blend of grains like wheat, rice, and corn. This variety from Tamanoi has a clean, subtly sweet, and less acidic profile compared to Western vinegars, making it a fundamental component in Japanese cuisine. It is commonly used to season sushi rice, providing the characteristic tang and sheen that balances the richness of the fish. You can also use it to create light salad dressings, tangy marinades for meat and fish, or quick pickles (sunomono). For perfect sushi rice, gently fold the vinegar into freshly cooked short-grain rice while it's still warm, allowing the grains to absorb the flavour evenly. This staple ingredient is a cornerstone of any Japanese pantry, suitable for both experienced cooks and those new to Japanese flavours.