In a large bowl or container, combine soy sauce, mirin, ryorishu, sugar and oil. Add chicken wings and make sure they are coated well with the mixture. Cover with plastic wrap or lid and place in fridge for a couple of hours to marinade. Overnight is preferable, but if you don't have the time at least 2 hours.

Pre-heat oven at 180 degrees C. Remove your chicken wings from the bowl/container, reserving the marinade and place them on a baking tray which has been lined with baking paper.

While wings are cooking, brush a couple of times with marinade. I do this when I am turning the wings over to ensure a nice even colouring. Cook chicken wings in oven for approximately 45 minutes until cooked through and are deep golden brown in colour.