At each Lotteria store, the "last of the year" "excellent tower cheeseburger (5th tier)" will be on sale only on December 10th, which is "Lotteria Day". The single item price is 500 yen (tax included), and the sale starts at 10:30.
Apparently this year's last chance! (Source: Lotteria Official Twitter)
This product is a hearty menu with beef patty and cheese mixed in 5 layers and sandwiched with buns. You can choose from 2 to 5 tiers of patties, but the price is 500 yen including tax for any number of tiers.
Until December 14th, there is also
a Twitter campaign where you can win the "Exquisite Tower Cheeseburger Full-scale Mouse".