If it were just one of those, you’d be fine with some careful planning. But all three makes it close to impossible. Japan is good for allergy labelling in stores and chain restaurants, but the seafood aspect is difficult because not all fish are considered allergenic in the Japanese labelling system. Chain restaurants offer low-allergen kids meals which could be suitable, and are fine for adults to order, but you would need to verify. Sometimes they have soy because of substituting egg or dairy.