Uncovering the Unique Appeal of Unagi-imo, Born from Local Pride

There is a quietly growing interest in a unique Japanese sweet potato brand: Unagi-imo. With a name that is hard to forget, this special potato originates from Hamamatsu—a city known for its unagi (eel) culture. It was born out of one man’s passion for agriculture, combined with the distinctive characteristics of the local land and culinary traditions.

In this article, we delve into the origins of Unagi-imo, uncover what makes it truly one-of-a-kind, explore its flavor and craftsmanship, and introduce the shops where you can enjoy it for yourself.

A Mission Rooted in Recycling and Solving Local Issues

The story of Unagi-imo begins with Mr. Ito, a local entrepreneur running a recycling business in Hamamatsu. While working with organic waste such as pruned branches and tree stumps to improve soil quality, he came face-to-face with the reality of an aging farming population. This experience inspired him to ask himself, “Is there something I can do to help?”

The crop he chose to grow was sweet potatoes. Why sweet potatoes? Hamamatsu’s unique sandy soil and Japan’s longest annual hours of sunshine create ideal conditions for large, flavorful sweet potatoes. However, starting from scratch came with challenges—no equipment, no farming know-how, and a market already filled with established producers made it difficult to gain a foothold.

That was when Mr. Ito turned his attention to unagi. Hamamatsu has long been known for eel farming and cuisine. He envisioned a way to reuse discarded parts of eels—such as heads, bones, and entrails—as a natural fertilizer.

Sweet Potatoes Grown with Eel-Based Fertilizer: The Birth of Unagi-imo

This is where the name Unagi-imo comes from. Normally, unused parts of eels are thrown away by restaurants. Mr. Ito decided to try converting these into fertilizer. However, eels contain a high amount of fat, which is unsuitable for direct agricultural use. After numerous trials and improvements, he developed a special fertilizer with just the right balance—rich in nutrients but with excess fat removed.

Using this fertilizer in the sandy, well-drained soils of the Enshū region and under abundant sunlight, a new kind of sweet potato was born. These potatoes are not only sweet but also rich in deep, complex flavors that set them apart.

The Surprising “Umami Components”

Many individuals who have tasted Unagi-imo have unanimously remarked, “This sweet potato possesses umami.”
When speaking of sweet potatoes, the common points of evaluation tend to focus on sweetness and a fluffy texture. However, Unagi-imo distinguishes itself by offering a remarkable depth of umami in addition to those characteristics.
Mr. Itō, astonished by such feedback, requested a local university to conduct a component analysis in order to identify the cause of this distinctive flavor.

As a result, it was discovered that Unagi-imo contains a higher concentration of amino acids—the very components responsible for umami—than ordinary sweet potatoes. This finding suggests that the enhanced nutritional value is not a mere coincidence, but rather a likely outcome of using eel-based fertilizer in cultivation.

In other words, the umami flavor of Unagi-imo can be described as a taste that is truly representative of Hamamatsu—a flavor born from the region’s culinary traditions and its naturally inspired agricultural practices.

 Brand Evolution and the Expanding World of “Unagi-imo Sweets”

Thanks to enthusiastic customer feedback and word-of-mouth acclaim, Unagi-imo quickly gained widespread recognition. Its popularity extended beyond local consumption, eventually leading to the establishment of an antenna shop in Tokyo. Today, its reach has expanded across borders, with annual exports to Taiwan, Hong Kong, Malaysia, Singapore, Thailand, and Canada.

↑This is a photograph of a booth showcasing Unagi-imo in Taiwan.

One of the key reasons Unagi-imo has garnered such affection lies in its expansion into the world of sweets. Mr. Itō developed Unagi-imo into powdered and processed forms, which he began supplying to confectionery shops within the city. As these sweet creations took form, Unagi-imo began receiving strong support from women and tourists alike, rapidly expanding its fan base.

At present, there is a rich variety of sweets such as “Unagi-imo Soft-Serve Ice Cream,” “Unagi-imo Mont Blanc Soft-Serve,” and “Unagi-imo Pudding.” These have steadily established themselves as must-try “local sweets” for anyone visiting Hamamatsu.

In addition, as part of its branding efforts, the official character “Unamo” was introduced. With an endearing appearance and a humorous personality, the character quickly gained popularity and earned the runner-up prize at the 2024 Yuru-Bāsu (Yuru-chara Grand Prix). Promotional activities are conducted mainly via social media, as part of a broader initiative to bring energy and vitality to Hamamatsu through Unagi-imo.

A restaurant in Hamamatsu where you can enjoy Unagi-imo.

In Closing: A Taste That Connects Hamamatsu to the Future

Unagi-imo is more than just a delicious sweet potato. It represents a community-driven effort, born from a passion for sustainability and local agriculture. By transforming discarded eel parts into a resource, and addressing regional issues such as aging farmers and abandoned farmland, Mr. Ito has created a product full of meaning and flavor.

If you ever find yourself in Hamamatsu, do not miss the opportunity to experience the one-of-a-kind taste of Unagi-imo—a symbol of innovation and hometown pride.

The best meal that you must eat when you go to Hamamatsu.