It's no secret that Japanese fast food chains like to get a little adventurous with the color and toppings of their burgers, but in recent years even Japanese sushi chains, particularly kaitenzushi (conveyor belt sushi) restaurants have been offering up some unusual ingredients and even sushi rice cola. So it should come as no surprise that sushi chain Sushiro is jumping on a trend that has caught on overseas with their own version of a sushi burger.

Unlike the sushi burgers you may have seen in other countries where sushi rice takes the place of the bun, this is actually a piece of sushi sandwiched between bread. Called the Saba Burger (Saba is mackerel), the burger makes use of an actual piece of nigiri sushi, in this case shime-sabe (vinegar pickled mackerel cured in salt) pressed over sushi rice, a shiso leaf, and a dollop of wasabi-mayonnaise. As Sushiro is a kaitenzushi chain, the burger is made fresh to order and than shipped to you on the convenience of a conveyor belt.

This isn't an especially different venture for Sushiro, who has been more than open to featuring departures from traditional sushi on their menu. For instance, their Ikebukuro location (which features the Saba Burger) has another exclusive menu item titled the "Roast Beef Mountain", which is topped with yogurt sauce.

That may look a bit wild to you to you, but maybe now would be a good opportunity to remind everyone that there is nothing about the definition of sushi that dictates a need to use fish, raw or cooked. Sushi is simply constructed from using shari (しゃり), or sushi rice, and neta (ネタ), the ingredient used as topping. While obviously most good old fashioned sushi makes use of raw toppings, it's not uncommon to to see cooked toppings, and even crazier ones like the Roast Beef Mountain, which are usually made to be kid-friendly, as children sometimes take a bit longer developing a taste for sushi.