Preparing the rolls: Lay a slice of beef flat on a clean surface. Place 1-2 pieces of scallion on one end of the beef slice and roll tightly to encase the scallions. Repeat with the remaining beef slices and scallions.

Preparing the sauce: In a small bowl, mix soy sauce, mirin, sake, sugar, and grated ginger until the sugar dissolves. Set aside.

Cooking the negimaki: Heat vegetable oil in a skillet over medium heat. Place the rolls seam-side down in the skillet and cook for 1-2 minutes until browned. Turn the rolls gently to brown all sides evenly, about 6-8 minutes in total.

Glazing with sauce: Once the rolls are cooked, pour the prepared sauce into the skillet. Reduce the heat to low and let the rolls simmer in the sauce, turning occasionally to coat them evenly. Cook for 2-3 minutes until the sauce thickens and clings to the rolls.

Serve: Remove the Negimaki from the skillet and slice each roll into bite-sized pieces. Arrange on a serving plate and drizzle with any remaining sauce from the pan. Negimaki is ready to enjoy! Serve warm as an elegant appetizer or alongside rice and vegetables for a complete meal.