Mix together shoyu, sake, sugar, sesame oil, and garlic powder together. Taste and change according to preference.
Put ground beef in a bowl and add shoyu mix and incorporate. Let sit to soak up the juices.
Rehydrate the cellophane noodles by putting the noodles in a bowl and adding hot water, letting them soak for a few minutes. Drain and, if need be, cut noodles to bite-size pieces.
Put pan on med heat and wait for the pan to get hot. Put ground beef in and stir occasionally. When the ground beef is almost cooked but not quite done, add carrot and bean sprouts. Stir and cook until beef is done.
Pushing the meat and veggies to the side, add the noodles, stirring around to soak up all the juices left. Transfer noodles, beef, and veggies onto a plate to let cool. Once cool, pack into respective bentos and garnish with green onions.
Recipe by SmartSexyPaleo at https://smartsexypaleo.com/korean-stir-fry-japchae-recipe-%e7%84%bc%e3%81%8d%e3%83%81%e3%83%a3%e3%83%97%e3%83%81%e3%82%a7/