In a small saucepan, combine soy sauce, mirin, sake, sugar, and water. Place over medium heat and stir until the sugar dissolves completely. Allow the sauce to simmer gently for about 10 minutes until slightly thickened. Remove from the heat and set aside to cool.

Preheat a charcoal grill or grill pan to medium heat. Lightly brush the grill with vegetable oil to prevent sticking. A traditional Japanese unagi grill imparts a delicate smokiness that defines the dish.

Place the eel fillets in a bamboo steamer or over a heatproof plate and steam for 5–7 minutes. This step softens the flesh and reduces excess oil, ensuring a smooth, melt in the mouth texture before grilling.

Lay the steamed eel skin side down on the grill. Cook for 5–6 minutes until the surface begins to brown lightly. Avoid moving the eel too much to prevent it from breaking apart.

Brush the eel generously with the tare sauce, then flip carefully using tongs or a wide spatula. Brush the other side and continue grilling for another 3–4 minutes. The sugar in the sauce will begin to caramelise beautifully.

Continue brushing and grilling the eel for another 5–7 minutes, turning occasionally. Each layer of glaze deepens the flavour and adds shine. The goal is a glossy, lacquered surface with lightly crisped edges.

While the eel finishes cooking, portion freshly steamed rice into four bowls. Keep the rice warm and slightly firm, as it complements the rich sauce of the eel perfectly.

Give the eel a final brush of sauce just before removing it from the grill. Allow it to rest for 2 minutes to let the juices settle and the glaze set evenly.

Using a sharp knife, cut the eel fillets into neat portions. Traditionally, they are sliced diagonally for elegant presentation and easy eating.

Lay the eel slices over bowls of rice and drizzle lightly with extra sauce. Sprinkle with a pinch of sansho pepper if desired. Serve immediately while hot, accompanied by pickles or miso soup for a complete meal.