Both the bun and cheese have tomato powdered mixed in to achieve the burger's signature red color. The sauce is a spicy blend of chili peppers and miso based on Chinese doubanjiang (chili bean paste/sauce).
The Red Samurai is available in both chicken and burger versions. The chicken version adds a crispy chicken patty, tomato, lettuce, and mayo, while the burger version adds a flame-grilled burger patty and grilled slice of onion.
The red burger is the second colored burger from Burger King in Japan. They first explored the colored burger concept in 2012 with the Black Burger, which featured a black bun, black cheese, and, yes, a black sauce. The Black Burger is slated to make a return later this summer in August.