Takoyaki (octopus balls). It was annoyingly hard to find but the location on the map is correct.
Apparently their most popular version is the one with green onions on top but I didn't know this until after I went, so I'll need to go back. I enjoyed the standard version anyway.
They cost 70 yen each and come in plates of either 6, 8 or 10. Add on 100 yen per plate to have the green onions.