Begin by peeling the daikon radish and slicing it into thin rounds or matchsticks.

In a mixing bowl, whisk together the rice vinegar, sugar, salt, and water until the sugar dissolves.

Place the sliced daikon into a clean glass jar, packing it tightly.

Carefully pour the brine over the daikon slices until they are fully submerged.

Seal the jar with a lid and place it in the refrigerator.

Let the pickled daikon sit in the refrigerator for at least 4 hours before tasting.

Once ready, serve the pickled daikon as a side dish or condiment.