Step 1

In a large bowl, whisk together the shoyu, mirin, sake, dark soy sauce and sugar until well combined. Add the steak and massage the marinade into the meat.

Step 2

Heat a medium skillet over high heat until very hot. Brush the pan with oil, and then add the steak, reserving the marinade. Sear until well charred and caramelized on both sides, adjusting the heat as needed, 3 to 4 minutes per side.

Step 3

About 1 minute before your steak is cooked to your liking, add the ginger and scallions to the pan and briefly sear, then pour in the marinade and allow to boil vigorously for 30 to 60 seconds, or longer, depending on how well done you want your steak. (An instant-read thermometer inserted from the side into the thickest part of the meat should register 130 to 135 degrees for medium-rare.)

Step 4

Transfer the steak to a cutting board and let rest for 2 to 3 minutes, then slice against the grain into thin strips. Transfer the steak to a serving platter. Heat the marinade for about 1 minute, then pour it over the steak and serve.