I've listed 1 rice cooker cup worth (before cooking) of rice, but use as much as you need depending on how much you need.
Incidentally, I filled a 880 ml and 500 ml capacity bento box (excluding the spaces for the sides) with 650 g of rice!
To prevent the rice from getting greasy, stir fry the ◎ ingredients with just a little oil (use anything you like). Add the ketchup.
Stir fry while making sure you don't scorch it. I think you will need about 2 tablespoons of ketchup per 1 rice cooker cup worth of rice (350 g when cooked). Throw in the rice!!
The rice will turn ketchup-colored. Add the chicken soup stock granules to finish. Add 1 tablespoon per 1 rice cooker cup worth of rice.
If you add too much ketchup, the rice will be soggy. The ketchup will just lightly color the rice. The chicken stock granules will flavor the rice.
Other dishes you could pack in your bento along with the rice is this mentsuyu katsudon (pork cutlets on rice with sauce) Recipe ID: 2121154. The rice won't become soggy.
Make omurice with scrambled eggs Recipe ID: 2120818.
Story Behind this Recipe
You may measure sugar or soy sauce, but do you measure ketchup with measuring spoons? So long as the rice is tinted a light pink, it should be ok. Isn't it hard work to split a soup stock cube in half? This is what I was thinking when I came up with this recipe.
For the ◎ ingredients, use chicken or whatever you like. But if you add onion, the rice will become somewhat soggy. The key is to stir fry the added ingredients and ketchup together before adding the rice. Spaghetti Napolitan is made in the same way.