Wash the blackberries thoroughly and remove the stems. Place the washed blackberries into sterilized jars or containers, leaving a little space at the top.

In a medium-sized saucepan, combine Marukan Genuine Brewed Rice Vinegar, granulated sugar, water, and vanilla extract.

Place the saucepan over medium heat and bring the mixture to a simmer, stirring occasionally to dissolve the sugar. Once the sugar is completely dissolved, remove the pan from heat. Allow the pickling liquid to cool to room temperature.

Once the pickling liquid has cooled, add the liquid to the blackberries, ensuring they are completely submerged.

Seal the jars or containers tightly and place them in the refrigerator. Allow the blackberries to pickle for at least 24 hours before using to allow the flavors to develop.