Nikka Black Deep Blend Extra Sweet looks to be the latest variation of budget-friendly blended whisky out of Nikka, slated for release on or around September 11. It has just popped up on Amazon JP for a 2,138 yen, so a 700 yen premium over standard Nikka Black Deep Blend (based on Amazon JP prices).
This release follows in the footsteps of Nikka's other Limited Edition blends, such as May 2018's Nikka Black Rich Blend Extra Sherry, and last year's Nikka Black Aromatic, among others. I guess they're doing one every 4-5 months now? "Extra Sweet" generally isn't something I look for in a whisky, but as always, drink what you like!