Dissolve the salt in the water. Place the daikon in a crock and add enough salt water to submerge, making additional brine as needed. Place weights on top to fully submerge and let rest at room temperature 24 hours.
Combine the remaining ingredients in a small bowl.
Remove the daikon from the brine and wipe off excess moisture. Pour half of the shio koji mixture in the bottom of a resealable container or crock. Place the daikon on top in a single layer. Top with the remaining shio koji mixture, spreading equally. Cover and let sit at room temperature for 3 hours, then refrigerate for 3 days before use. Remove the daikon from the brine when pickled to your liking.