Trim the ends of the okra and remove the calyx. Rub with 1/3 tsp salt and rinse under water. Drain well. Wash the nameko mushrooms thoroughly and drain.

Boil water in a pot and cook the okra for 1 minute. Transfer to cold water, cool, and drain. Slice into 1cm pieces.

Reboil the water and cook the nameko mushrooms for 1 minute. Drain and let cool.

Remove the seed from the ume plum and mash it into a paste using a knife.