"Blueberry cheeseburger" is sold at each hamburger chain "Freshness Burger" (excluding some stores). The sale period is until February 28th. The price is 480 yen (excluding tax).
This is an adult-style fruit burger with beef patty, bacon, crushed blueberries, and refreshing sour cottage cheese topped with balsamic sauce.
It seems that it is a product unique to Freshness, which has sold unique fruit burgers such as "Mango Burger" and "Peach Burger" in the past.