Cut the flank steak across the grain into 1/4-inch-thick slices. Thread the meat onto 8-inch bamboo skewers and arrange the skewers side by side on a large platter.

Combine the sake, tamari, sesame oil, honey, garlic, ginger, scallions, five-spice powder and pepper in a small bowl. Pour the marinade over the skewers and turn to coat. Let the beef marinate at room temperature for 30 minutes or refrigerate for up to 1 hour.

Prepare the grill. Place the grate 6 to 8 inches from the heat source. Lightly brush the grate with oil. Light the grill.

Arrange the skewers on the grate and grill over high heat, turning once, until sizzling and nicely browned all over, 6 to 7 minutes.

Transfer the skewers to a large platter. Serve with peanut sauce.