MOS Burger Joins the Chiba Soy Sauce Gourmet Fair 2026 for a Second Year
MOS Food Services, Inc. (President: Eisuke Nakamura; Head Office: Shinagawa-ku, Tokyo), operator of the MOS Burger chain, will launch the “Kuro Ajillo Cheeseburger” (630 yen) on Thursday, October 1, 2026 at all 80 MOS Burger locations in Chiba and Ibaraki Prefectures, as a limited-quantity, region-exclusive item. Packed with Chiba-grown ingredients such as soy sauce and bacon, the burger also marks the company’s participation in the “Chiba Soy Sauce Gourmet Fair 2026,” which begins on the same day.
Chiba: A Soy Sauce Powerhouse Accounting for Over 35% of National Shipments
Chiba Prefecture is one of Japan’s leading soy sauce production areas, accounting for more than 35% of national shipments. Beyond soy sauce, fermentation culture runs deep in the region, with mirin producers, sake breweries and dairy farming all firmly rooted in local life.
Last year, in order to spread the word about the deliciousness of Chiba’s local ingredients through soy sauce, the prefecture held the “Chiba Soy Sauce Gourmet Fair 2025” for roughly a month and a half starting on “Soy Sauce Day” (October 1). A total of 338 restaurants, including MOS Burger, took part.
As a hamburger chain born in Japan, MOS Food Services continues to develop products that make use of regional ingredients and honor Japan’s unique food culture. This marks its second consecutive year joining the fair, supporting Chiba’s goal of creating new food culture and promoting local cuisine, while giving loyal customers a chance to savor delicious local ingredients.
What Makes the Kuro Ajillo Cheeseburger Special
The star of this burger is “kuro ajillo” (black ajillo), a local specialty unique to Chiba. Created by adding soy sauce to ajillo, the Spanish dish of ingredients simmered in olive oil and garlic, it delivers a deep, layered flavor and fragrant aroma — now reimagined in burger form.
Carefully Crafted Components
- Patty: Paired with cheddar-based sliced cheese for added richness
- Vegetables: Juicy tomato and crisp lettuce for a refreshing balance
- Kuro Ajillo Sauce: A special sauce built on Chiba-produced soy sauce, simmered with Chiba-raised pork bacon, mushrooms, zucchini and basil
The use of richly savory bacon made from Chiba-raised pork gives the sauce a firm texture and satisfying bite. The toasty depth of soy sauce combined with the richness of garlic and olive oil creates a multi-dimensional flavor unlike any previous MOS burger.
*The cheese is heat-processed at the factory.
Product Details
- Product & Price: Kuro Ajillo Cheeseburger (630 yen, tax included)
- Sales Period: Thursday, October 1, 2026 – mid-November *Limited quantity (while supplies last)
- Locations: All 80 MOS Burger stores in Chiba and Ibaraki Prefectures
- Participating Event: Chiba Soy Sauce Gourmet Fair 2026
With sales restricted to just 80 stores in Chiba and Ibaraki and quantities limited, the burger will end once stocks run out. Given the short run of about six weeks from Soy Sauce Day on October 1, an early visit is recommended.
“Making People Around the World Happy Through Food”
MOS Food Services consistently delivers products grounded in its philosophy of “deliciousness, safety and health,” served with “sincere and smiling service.” Through its after-order cooking policy maintained since founding and product development that values Japanese food culture, the company says it will continue to pursue its mission of “making people around the world happy through food.”
This is a burger only a chain that grows alongside its communities could create. This autumn, why not try the Kuro Ajillo Cheeseburger, where Chiba’s soy sauce heritage meets Spanish cuisine?