Shellfish Allergy while Traveling in Japan

I have a severe Shellfish Allergy to any crustaceans. I can eat any sort of fish, clams, oysters or mussels but I cannot eat crab, lobster, shrimp, crayfish or anything made with broth from these types of shellfish. I am very nervous since I have heard that in Japan the dashi can be made from shellfish and most all types of foods start with a dashi base. I have even heard that most restaurants will tell you there is no shellfish in something since they don't count the dashi or broth as being shellfish even though it may have been made with those. I am traveling with two doctors and have Epi-pens and Benadryl ready but I would really like to avoid an attack if possible. Can you recommend my best course of action? Should I bring a printout specifying my allergy in Japanese to show to waiters or would pictures be better to describe it? I have heard that there are different words in Japanese for shellfish so sometimes it is confusing to explain. Also, are there any types of foods you would recommend so that I'm sure to be clear of it?
Thank you so much!
Athena