1. In a bowl, add all ingredients B and marinate the chicken for about 15 to 30min.
2. In a saucepan, add all ingredients A and bring it to a boil. Reduce the heat to low. Cover and simmer for about 30min. Take the skin off (if not done yet). Set aside.
3. In a skillet, heat 1 tbsp vegetable oil and cook the leek until wilted or lightly brown. Transfer to a plate and set aside.
4. In the same skillet, heat 1 tbsp oil and cook the chicken until golden brown, then flip them and brown the other side. Turn the heat to medium-low and add the sauce from #2. Simmer the chicken in the sauce, occasionally turning to coat it well until the sauce has thickened.
5. Add the leek and fry for a few more minutes.
6. Serve hot steamed rice into serving bowls. Add Yakitori on top of the rice!