Kasama has Kasama Inari shrine, and this sushi grew up outside its gates, sold to the people who had come there to pray.

The shrine was originally sited beneath a walnut tree, and is also called Kurumishita Inari, walnut-below Inari. On the strength of that one connection, inari sushi with walnuts inside started being sold here. It is a piece of reasoning I find entirely satisfying. The tree named the shrine, the shrine named the district, and then the district went and put the nut inside the food.

It did not stop at walnuts, either, once the idea had taken hold. Shops now fill the fried tofu pouches with buckwheat noodles, king oyster mushroom, chestnut, and various other things, and a version with soba inside instead of vinegared rice is called soba inari.

Which means that you cannot tell what you are holding until you have already bitten into it. Every shop has its own fillings, and not one of them is visible from the outside of the pouch. The seventeenth day of every month has been officially designated Inari Sushi Day here. A local specialty that runs on a pun about a tree, and remains genuinely unpredictable at the level of individual pieces.