Confirm the tuna is sushi-grade and very cold. Keep it refrigerated until just before slicing. Pat the tuna dry with paper towels to remove excess moisture for cleaner slices.

Trim

Using a very sharp, long knife (sashimi or chef's knife), trim away any discolored edges, bloodline, or sinew. Work quickly to keep the fish cold; hold the tuna on a bed of ice or a chilled plate if room temperature rises.

Optional quick marinade

If using the optional marinade, whisk mirin, rice vinegar, grated ginger, and minced garlic in a small bowl. Brush one side of the tuna lightly (about 30–60 seconds per side) and let rest on a plate for 1–2 minutes — do not soak or leave more than a few minutes to preserve sashimi texture.

Slice

Hold the knife at a slight angle (about 20–30 degrees). Using a single smooth motion, slice the tuna into 1/4-inch to 3/8-inch (6–9 mm) thick slices for sashimi. Aim for uniform slices about 1 to 1.5 inches wide. Wipe the knife with a damp cloth between cuts to keep slices clean.

Season

Arrange slices on a chilled serving plate in a fan or staggered stack. Lightly sprinkle sea salt and a tiny pinch of freshly cracked black pepper over the fish. If using toasted sesame oil, drizzle very sparingly (a few drops) over the slices or the plate edge.

Accompaniments & Garnish

Pour soy sauce into a small dipping dish. Place a small dollop (about 1/4 to 1/2 tsp) of wasabi on the side of the soy sauce or on the plate beside the sashimi. Arrange pickled ginger, lemon/lime wedge, scallions, sesame seeds, and microgreens or shiso leaves attractively around the fish.

To serve: For each bite, optionally add a tiny smear of wasabi to a slice or mix a small amount into soy sauce. Lightly dip tuna into soy sauce (do not soak). Eat with pickled ginger between bites to refresh the palate.