Heat a pan over medium/low heat. Add the sesame seeds to the pan and toast just until fragrant 1-2 minutes. Be careful not to burn them! Remove from the pan and let cool. Next toast the bonito flake for the same amount of time, just until fragrant. Remove the bonito and let cool. Last toast the nori in the same pan, about 1 minute on each side until it's very crisp.
Crumble the toasted nori into the base of a blender along with the bonito flake. Use the pulse setting and a combination of blending on high and low to achieve a fine flakey consistency.
Pour the blended nori and bonito into a bowl and toss with the toasted sesame seeds and sugar until evenly combined. Transfer to a jar with a tight-fitting lid, store in a cool, dry place out of direct sunlight for up to two months.
Notes
This recipe can also be made in a food processor however that may result in a coarser seasoning which is totally fine!