Place the hamachi in the freezer for about 10 to 15 minutes. This makes it easier for slicing.
In a small bowl pour in the ponzu, tamari, lime juice, mirin, yuzu kosho and sesame oil and whisk to combine.
Remove the hamachi from the freezer and using a sharp knife, slice the hamachi thinly, season very lightly with kosher salt.
Scatter the slices onto a platter, plate or serving dish.
Assemble the cucumber, radish, serrano and cilantro over top of the hamachi.
Drizzle the dressing over top and garnish with sesame seeds.
Serve immediately and enjoy!
