Gather all ingredients.

Soak uncooked rice in water to cover for 4 hours; drain and rinse.

Bring 2 cups water to a boil in a medium saucepan. Add rice and stir. Reduce heat, cover, and simmer for 20 minutes.

Remove pan from heat and stir in rice vinegar. Set aside to cool.

Stir sugar, soy sauce, and oyster sauce together in a medium bowl until sugar is completely dissolved.

Slice luncheon meat lengthwise into 10 slices, or to desired thickness, and marinate in sauce for 5 minutes.

Heat oil in a large skillet over medium-high heat. Cook slices until lightly browned, about 2 minutes per side.

Cut nori sheets in half and lay on a flat work surface.

Place a rice press in the center of a sheet, and press rice tightly inside.

Top with a slice of luncheon meat, and remove press.

Wrap nori around rice, sealing edges with a small amount of water. (Rice may also be formed by hand in the shape of the meat slices and about 1-inch thick.)

Serve musubi warm or chilled.