This tekkamaki is an Edomae-zushi (hand-rolled sushi) which uses tuna but is wrapped with a sheet of dried seaweed, so people can eat it without using chopsticks or getting their hands dirty.
この鉄火巻はマグロを用いた江戸前寿司でありながら、海苔で巻かれているので、食べるのに箸も要らず手も汚さない。