We now offer food-safe clear urethane coating service for all wood bento boxes made by Shibatatoku.   Cost is $22 for each box. 
 
The urethane we use is a Japan-made product and it is certified food-safe.  Once coated, the bento box wood surface will become water-resistant, making cleaning and drying more convenient and you won't have to worry about sauces staining the wood anymore.  Urethane coating is clear and matte, but expect the color of the wood will become slightly darker than raw finish.  This color change is very slight that most people couldn't tell the difference.  Tactility-wise, you can feel a smooth plastic skin over the surface of the wood.  
 
After coating, the wood bento box will no longer have the natural aroma of cedar wood and the ability to absorb and balance moisture for rice/bread will be depleted.
 
Another alternative for finishing the wood to make it water-resistant would be traditional Japanese urushi lacquering.  Japanese lacquer has a rich dark caramel tone, giving it a completely different aesthetics. Inquire to learn more.