Heat water, sake, and salt in a pot. Once boiling, add chicken thigh and boil for 10 minutes. Turn off the heat and let it sit for 30 minutes to cook through residual heat.

Cool the chicken in the refrigerator for 2 hours, then slice thinly into 1cm pieces.

Cut scallions into small pieces and slice cucumber thinly into strips.

Mix sugar, vinegar, soy sauce, sesame oil, and broth in a container to make the sauce.