To make the teriyaki marinade, add shoyu, sugar, mirin, garlic, and ginger into a bowl and whisk together. Transfer the marinade to a sauce pan and heat just to warm up slightly until sugar is dissolved. Don't boil or overheat the marinade.

Cut steak against the grain into thin slices.

Add steak, sliced green onion, and marinade to a large bowl and stir to combine. Refrigerate for at least 4 hours.

Preheat your griddle on low. Or, you can also cook your Hawaiian beef teriyaki in a skillet on your stovetop.

Add the pieces of marinated steak to the griddle, spacing them out so as to not overcrowd the griddle.

Once you add the meat to the griddle, let it cook untouched for about 2 - 3 minutes. Then saute it for a minute or two and spread it back out on the griddle. When you spread out the meat on the surface while it's cooking, it allows the sauce to reduce more quickly. Continue this process, mixing it together and then spreading it back out to continue to cook.

Cook until the steak is done and the sauce has reduced a good bit.

Remove the Hawaiian beef teriyaki from the griddle and serve with white rice or your favorite side dishes.