Just Bento

There's a program in Japan called Nihonjin Test with lots of great household tips, unfortunately my husband wasn't with me at the time this question came up so I could only get a basic grasp of what was going on (I don't speak Japanese).

Anyway, I found a mention of this program and shoyu stains on the internet
服についた醤油のシミを素早く落とすためには砂糖水を使う

水1ℓに砂糖小さじ2杯を溶かしスポンジに含ませ下にタオルを敷きシミの部分をたたく

What this says is that you dissolve two teaspoons of sugar in one litre of water. Put the stained item onto a towel and apply the sugar water onto the stain with a wet sponge. Keep patting at the stain and it should transfer onto the towel.

However, this isn't what I remember... I recall something to do with soy sauce stains and direct sunlight. If anyone knows more about this tip I'd love to have my curiosity about it finally sated!

If all else fails, try this if you can get it where you are. It's pretty good at most stains.

Also, see http://housekeeping.about.com/od/stainremoval/a/stains_soysauce.htm

I have seen all kinds of suggestions for removing soy sauce. I have no idea if these will work...but worth a try maybe! (The best thing to do with soy sauce stains is to soak up as much as you can ASAP...even sucking out the stain if it's a favorite shirt or something (hey disgusting perhaps but works!) Then regular laundering should remove the residue.)

- Put droplets of clear vinegar (not like red wine vinegar, obviously!) on the soy sauce stains. Take an old clean toothbrush and tap on the stains while occasionally stopping to absorb the moisture with a paper towel. In time the stains should disappear.
- This one looks like a variation of the sugar-water one Loretta suggested. Dissolve 10g (2 tsp) of salt in 1/4 cup of warm water, and 2g (about 1/3 tsp) of sugar in another 1/4 cup fo warm water. Put a padding cloth under the textile you want to clean, to absorb excess moisture. Apply drops of the salt water first to the stain and tap/brush the stains with an old clean toothbrush. Leave for 1/2 an hour, then repeat the process with the sugar water. Launder the item as usual.
- use one of those stain remover things (they come in a solid form or in a tube) and apply directly to the stain. Wash the stain until it's almost faded then launder the item as usual.
- Try rubbing soap on the stain and washing and scrubbing by hand until almost faded, the launder as usual.
- Bonus: If the soy sauce is on a solid surface like a wall, try scrubbing with a little toothpaste until the stain is gone. May work on some fabrics too.