Another Japanese favorite! My wife is now torn between Gyudon and this. For this dish I was able to use Powdered Dashi (Ajinomoto brand). I was able to buy it at Robinson's Supermarket. This is again based on a YouTube video, the same presenter from the Gyudon I made (cookingwithdog).
http://www.youtube.com/watch?v=QMJY29QMewQ
Still didn't have Sake but I did use Chinese rice wine as a substitute.