Combine the soy sauce, sake and sugar in a small saucepan and heat gently to dissolve the sugar. Leave to cool completely. Place the chicken in a shallow dish, add the marinade and leave to marinate for at least 1 hour.
Soak 8 bamboo skewers in cold water for 30 minutes. Mix the mayonnaise and wasabi paste together in a bowl, then cover and set aside until required.
Thread the chicken on to the skewers and cook on a hot barbecue for 2—3 minutes on each side until cooked through. Serve with the wasabi mayonnaise for dipping.