They're calling it the "Bistro-Style Hamburger Sandwich."
If you feel that "Hamburger Sandwich" is a bit redundant, hamburger or "hamburg" is a popular dish in Japan that's more like meatloaf or Salisbury steak than your typical hamburger patty. Like Salisbury steak, it typical comes with a brown sauce or gravy.
The Bistro-Style Hamburger's hamburger patty is thick and covered with a mushroom demi-glace sauce. It is accompanied by lettuce and what seems to be an au gratin sauce (the translation is a little confusing) on a whole wheat bun.
It's set to release on February 5, 2015 for 490 yen ($4.16 US) per sandwich.
It's the first time I've seen an entree at KFC feature something other than chicken. Shouldn't they change KFC to KFP&B or something while the sandwich is around?