If sesame seeds aren’t toasted, heat a dry skillet over medium-low and toast white and black sesame seeds together for 3–5 minutes, stirring constantly, until fragrant and lightly golden. Transfer to a plate to cool.
Tear or snip nori sheets into small, flaky pieces by hand or kitchen shears.
In a medium bowl, combine cooled sesame seeds, nori pieces, bonito flakes, granulated sugar, and sea salt. Stir until evenly mixed.
Transfer seasoning to an airtight container. Store in a cool, dry place for up to 2–3 weeks.