Put all the ingredients in a pot, apply heat and boil. It tends to bubble over, so be careful. Aim for medium heat.
Once it's boiled like in the picture - if you cut a line through the pan and it gels back in place, it's good. Aim for the texture of caramel sauce.
Once the temperature drops, it becomes sticky. It should be lightly syrupy.
The ratio of the ingredients is as follows: soy sauce : sugar : mirin : sake, 5:3:1:1. As long as you follow this ratio, you can use cups, ladles, etc.
Also works for tempura.
You could also use it to season tempura rice balls.
Story Behind this Recipe
I adjusted the amounts to tablespoons.
When cooking, if it's over high heat it'll bubble over, so be careful. If measuring by the spoonful or ladleful, the key is to start with the sugar (before it gets soggy with the soy sauce and wet ingredients).