7-Eleven, the ubiquitous convenience store (konbini) chain found throughout Japan, is launching a new “onigiri” (rice ball) exclusively in Hokkaido, the northernmost island of Japan. The new addition to the lineup is the “Giant Rice Ball: Ma-konbu & Yamawasabi (Horseradish) Mayonnaise,” which generously features “early-harvest Ma-konbu” kelp from the southern Donan region. Sales will begin sequentially at 7-Eleven stores across Hokkaido starting April 7, 2026.
This new product is a satisfying, hearty meal that allows you to enjoy the bounties of Hokkaido’s rich seas in the palm of your hand. The star ingredient, “early-harvest Ma-konbu,” is a resource that hasn’t been fully utilized until now. By pairing it with Hokkaido’s beloved “yamawasabi” (mountain horseradish) and creamy mayonnaise, 7-Eleven has created a flavor profile that is both unique and deeply satisfying.
Essential Info: Giant Rice Ball with Ma-konbu & Yamawasabi Mayo
This product is a regional specialty available only at 7-Eleven stores in Hokkaido. Here is the key information to check before you head out to grab one:
- Product Name: Giant Rice Ball: Ma-konbu & Yamawasabi Mayonnaise
- Price: 298 yen (321.84 yen including tax / approx. $2.15 USD)
- Release Date: Starting sequentially from Tuesday, April 7, 2026
- Sales Area: 7-Eleven stores within Hokkaido, Japan
Priced at approximately 322 yen ($2.15 USD), this item belongs to the “Giant Rice Ball” (Ookina Omusubi) series, which is significantly larger than standard onigiri (typically around 4 oz or 110g). Its substantial size makes it perfect for a full lunch or a very filling snack.
The Secret of Southern Hokkaido’s “Early-Harvest Ma-konbu”
The defining feature of this rice ball is the “konbu” (kelp) filling. Among the highest-grade “Ma-konbu” harvested in southern Hokkaido, this product specifically uses “early-harvest” kelp.
Typically, kelp is harvested only after it has grown to full size. However, during the cultivation process, a step called “thinning” is necessary to remove some young kelp to ensure the rest has enough space and nutrients to thrive. This young, thinned-out kelp is what we call “early-harvest Ma-konbu.” While its uses were limited in the past, it is actually incredibly tender, making it an ideal ingredient for rice ball fillings.
The smooth texture and the deep, refined umami flavor unique to Ma-konbu are at their peak in this early-harvest version. This initiative, which transforms a previously underused regional resource into a delicious new product, is also a win for environmental sustainability.
A Hokkaido Original: Yamawasabi meets Mayonnaise
Enhancing the umami of the kelp is “yamawasabi” (mountain horseradish), a staple in Hokkaido households. Unlike the common green “hon-wasabi,” yamawasabi is characterized by a sharp, refreshing spiciness that clears the sinuses.
By combining this pungent horseradish with mellow mayonnaise, the sharp heat is perfectly tempered while adding a rich depth of flavor. The harmony between the tender kelp, the spicy kick of the horseradish, and the smooth mayonnaise ensures that even with its giant size, you’ll enjoy every last bite.
A Sustainable Treat Protecting Regional Bounty
7-Eleven is actively working to reduce food loss by effectively utilizing local ingredients, and the adoption of “early-harvest Ma-konbu” is a key part of this effort.
By focusing on an underutilized material that rarely reached the market and transforming it into something of “delicious value,” the company has balanced environmental consciousness with an affordable price point. Consuming local ingredients without waste helps protect Hokkaido’s fertile seas and supports the local community. It’s a wonderful cycle where enjoying a delicious meal results in a positive social contribution.
Experience the Bold Flavors of Hokkaido at Lunchtime
This new rice ball is a special treat available only to those living in or visiting Hokkaido. The briny scent of the southern seas paired with the sharp zing of mountain horseradish perfectly complements the natural sweetness of the Japanese rice.
If you find yourself at a 7-Eleven in Hokkaido, be sure to pick one up and feel its impressive weight for yourself. Eco-friendly and, above all, delicious—this giant rice ball is the perfect modern meal to leave you feeling happy and satisfied.
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