Customers like Shigeaki Yamaguchi may be the last hope for McDonald's Japan as it battles slumping sales in the wake of an embarrassing string of food scandals.

At a location in Tokyo's busy Shinjuku district, Yamaguchi munched on the chain's newest culinary offering -- french fries drizzled in brown and white chocolate syrup.

"Delicious," the 37-year-old proclaimed as he dug into the sticky 330 yen ($2.90) mass known as the McChoco Potato.

"The reason I came is that I wanted to taste products that didn't exist until now."

Love them or hate them, social media spun into a frenzy over chocolate fries, and customer numbers rose in January for the first time in several years -- just as the salty-sweet creation launched.

"The chocolate fries have been extremely popular with customers, and actually not just customers in Japan," the unit's president Sarah Casanova said last week.