The thin slices of beef are stir-fried with onions and spring onions in an excellent sweet and savoury sauce. I swear there's red wine in there but no one would confirm it (the staff just repeatedly told me that it's their "special sauce"). Anyway, all that matters is it's yummy!
This forms a good value set meal too with rice, miso soup, pickles, a small side dish of mashed up cooked salmon and tobiko patty, and fruit included.