Thinly slice cucumber and sprinkle with 1/4 tsp salt. Let sit for 5 minutes, then squeeze out excess water. Slice shiso leaves finely and dice Nara pickles into 1cm cubes.

Slice sea bream sashimi thinly using a flat angle with the knife.

Mix sugar, salt, and vinegar in a bowl to prepare sushi vinegar.

In a separate bowl, combine cooked rice with sushi vinegar and mix gently. Add Nara pickles, cucumber, shiso leaves, and sesame seeds, then mix evenly.