The old literature had no examples of counting sushi with a special counter suffix, 'kan,' and only had descriptions of counting as hitotsu (one piece), futatsu (two pieces) and so on, or ikko (one piece), niko (two pieces) and so on.
古い文献に「かん」という特別な助数詞で数えた例は見当たらず、いずれも1つ2つ、または1個2個である。