On a cold evening in Tokyo, the smell of a roasting sweet potato can stop you mid-stride. Yakiimo is the Japanese roasted sweet potato, and it asks for nothing but time. You will also see it written yaki-imo or yaki imo in English, but they all mean the same dish.
First, this guide explains what yakiimo is, which Japanese sweet potato varieties roast best, and how to make it at home. It also covers the science behind the sweetness, a short history, and where to buy yakiimo in Japan today.
What Is Yakiimo?
Yakiimo, written 焼き芋（やきいも）in Japanese, is a whole satsumaimo, or Japanese sweet potato, roasted slowly in its skin until the flesh turns soft and sweet. In other words, yakiimo is the general name of the dish. Ishi yakiimo, tsubo-yaki, and kamado-yaki, on the other hand, name the roasting method: hot stones, a clay pot, or a large hearth oven.
Quick Facts
- Japanese Name
- 焼き芋（やきいも, yakiimo）; stone-roasted versions are 石焼き芋（いしやきいも, ishi yakiimo）
- What It Is
- A whole Japanese sweet potato roasted slowly in its skin
- Ingredients
- Sweet potato only; no oil, sugar, or seasoning required
- Main Styles
- Stone roasting (ishi yakiimo), clay-pot roasting (tsubo-yaki), hearth roasting (kamado-yaki), and modern electric roasting ovens
- Popular Varieties
- Beni Haruka, Anno imo, Silk Sweet, Beni Azuma, Naruto Kintoki
- Best Season
- Late autumn and winter for stored, well-matured roots; chilled and frozen yakiimo sell year-round
What Does Yakiimo Taste Like?
Depending mostly on the variety, the flesh can be fluffy (hokuhoku), gently moist (shittori), or thick and sticky (nettori). Slow roasting also darkens and concentrates the sugary liquid that seeps through the skin, which gives the outside a deep, toasted aroma. As a result, people eat yakiimo as a snack, a light meal, or a simple dessert.
Is Yakiimo the Same as a Western Baked Sweet Potato?
Not quite. Japanese sweet potatoes usually have reddish-purple skin and pale yellow flesh rather than orange flesh, and yakiimo roasts longer and more gently, with no toppings expected. So “baked sweet potato” is a fair comparison, but “Japanese roasted sweet potato” is more accurate.
Why Yakiimo Tastes So Sweet
A raw sweet potato already contains some sugar, mainly sucrose, but not much of it. Much of yakiimo’s characteristic sweetness, though, develops through storage and slow cooking. Two processes are at work, so it helps to separate them.
Starch, Enzymes, and Slow Heat
First, heat gelatinizes the starch inside the potato. An enzyme called beta-amylase then breaks that starch down into maltose, a sugar. The enzyme stops working once the flesh gets too hot, though. Slow heating keeps the flesh in the useful range for longer, so more maltose forms before the enzyme gives up. Japanese cooking guides often highlight temperatures around 70°C (158°F), where gelatinization and enzyme activity can overlap. That is a useful explanation rather than one universal target, because cultivar, root size, storage history, and heat source all change the result.
Maltose is not the whole story, however. Researchers in Chiba Prefecture, for example, calculated the sweetness of roasted Beni Haruka from sucrose, maltose, glucose, and fructose, weighting each sugar by how sweet it tastes. In other words, both the sugar made in the oven and the sugar already in the root matter.
Why Stored Sweet Potatoes Taste Sweeter
Freshly dug sweet potatoes often roast up less sweet than stored ones. According to Japan’s national agricultural research organization, NARO, even high-sugar cultivars can taste only mildly sweet as yakiimo right after harvest. That is why growers cure and store their crop. Curing means holding newly harvested roots in warm, humid conditions so the skin heals and the roots keep better.
What the Research Found
In a NARO study, Beni Haruka harvested in mid-August and stored at 11 to 13°C (52 to 55°F) for about two weeks developed more sweetness and a stickier texture. Consumers also rated it above one-year-stored Beni Azuma. This was a controlled method for producers, however, not a home storage tip.
Harvest Season vs Yakiimo Season
Farmers harvest sweet potatoes from late summer into autumn. However, NARO notes that storage raises sweetness, so yakiimo usually tastes best from late autumn into winter. Supply also varies by region, cultivar, and retailer.
Yakiimo Buying Calendar
- Early autumnNewly harvested roots arrive, although flavor can be lighter and texture firmer.
- Late autumn to winterStored, cured roots reach shops, so this is peak yakiimo season.
- Spring and summerInstead, look for chilled yakiimo, frozen packs, and long-stored roots.
Best Sweet Potatoes for Yakiimo
Until the early 2000s, fluffy varieties such as Beni Azuma dominated, but tastes then shifted toward moist and sticky types, according to Akio Kariya of Japan’s potato and sweet potato promotion association (Imorui Shinkokai). In his 2015 account, Beni Haruka, a cultivar released in the late 2000s, had become the leading variety in the modern yakiimo market. Note, however, that the names below are not all the same kind of name. Some are registered cultivars, while others are regional brands or trade names.
| Variety | Type of Name | Texture | Best For |
|---|---|---|---|
| Beni Haruka (紅はるか) | Registered cultivar | Moist and sticky after storage | Creamy yakiimo, long slow roasting, first-time tasting |
| Anno imo (安納芋) | Name for Tanegashima-derived lines, including registered cultivars Anno Beni and Anno Kogane | Very sticky, almost custard-like | Dessert-like yakiimo, long slow roasting |
| Silk Sweet (シルクスイート) | Trademark for cultivar HE306 | Smooth and moist | Creamy yakiimo with lighter sweetness |
| Beni Azuma (ベニアズマ) | Registered cultivar | Fluffy and dry | Fluffy yakiimo, classic Kanto style |
| Naruto Kintoki (鳴門金時) | Regional brand based on Kokei No. 14 lines | Fluffy to slightly moist | Fluffy yakiimo with a chestnut-like character |
In short, choose Beni Haruka, Anno imo, or Silk Sweet for moist yakiimo, and Beni Azuma or Naruto Kintoki for fluffy yakiimo. Storage, root size, and cooking method still change the result.
Beni Haruka (紅はるか)
Beni Haruka is the variety you are most likely to meet in a Japanese supermarket roaster. Freshly harvested roots may taste less sweet and firmer than properly cured ones, however, which is why storage matters so much. For more on its breeding and storage, see our guide to the Beniharuka (Beni Haruka) sweet potato.
Anno Imo (安納芋)
Anno imo, the sticky sweet potato of Tanegashima, takes its name from an island in Kagoshima Prefecture, and it covers a group of local lines rather than one cultivar. Roasted slowly, the orange-tinted flesh turns so soft that many people eat it with a spoon.
Silk Sweet and Beni Azuma
Silk Sweet, a smooth and moist variety sold under a trademark, sits between the fluffy and very sticky styles. Beni Azuma, by contrast, is the classic fluffy potato of the Kanto region, with yellow flesh and little stringiness.
Other Varieties to Look For
Benikomachi, a rare floury sweet potato from Chiba, offers an old-fashioned fluffy texture. Few shops carry it, but it is worth seeking out if you prefer hokuhoku-style yakiimo.
How to Make Yakiimo at Home
You do not need a stone oven to make good yakiimo at home. A home oven at a moderate setting does the job, as long as you give it time. Traditional plain yakiimo also needs no oil, butter, sugar, or seasoning.
Yakiimo Ingredients
| Ingredient | Amount |
|---|---|
| Japanese sweet potato (Beni Haruka, Silk Sweet, or your choice) | 1 medium root, about 250 g (9 oz) and 5 to 6 cm (2 to 2.5 in) across at its thickest |
| Optional toppings | A pinch of salt or a little butter, to serve |
How to Make Yakiimo
First, scrub the skin under running water and pat it dry. Do not peel it, since the skin protects the flesh while it roasts.
Foil is optional. Wrapping keeps more moisture and also softens the skin. Roasting unwrapped, however, gives a drier, more aromatic skin with caramelized spots.
Next, place the potato on a lined tray. Roast at an oven setting of 160°C (320°F) for 90 to 120 minutes, and turn it once halfway. Thicker roots need longer, while slim ones may finish sooner.
A skewer should pass through the thickest part with no resistance, even at the very center. The potato should also yield gently when pressed with an oven glove. Never test with bare hands, and open foil carefully, because trapped steam can burn.
Let it rest for about 10 minutes, then split it open. Eat it plain, or add a pinch of salt or a little butter if you like.
Oven Setting vs Potato Temperature
These are two different measurements. The 160°C figure is the oven setting. The 70°C band mentioned earlier refers to the flesh inside the potato while it heats. In practice, a moderate oven simply lets the center pass slowly through that range. That is why “fully tender in the center” is the real finish line, not the clock.
Air Fryer and Microwave
An air fryer also works well for smaller roots. Just do not overcrowd the basket, and turn the potato partway through. Power and thickness both change the time, so rely on the skewer. A microwave, by contrast, cooks sweet potato quickly but usually cannot match the aroma and sweetness of slow-roasted yakiimo.
Roasting Over Charcoal or an Open Fire
Roasting over charcoal or an open fire is fun, but it belongs outdoors. Use a permitted, well-ventilated location, and follow your local fire rules. Keep the potatoes on a rack above the embers rather than in the flames, and turn them often so the skin does not burn through before the center softens.
Optional Variation: Chilled Yakiimo
For hiyashi yakiimo, a popular warm-weather version, simply cool the roasted potato promptly and refrigerate it covered. As it chills, the flesh then turns dense, almost like a pudding.
Storing, Freezing, and Reheating Yakiimo
Cool leftover yakiimo soon after cooking, store it covered in the refrigerator, and eat it within a few days. Also avoid leaving it at room temperature for long.
- Freezing: Cool completely, wrap individual portions, and freeze them.
- Thawing: Later, move a portion to the refrigerator and let it thaw there.
- Reheating: Heat until hot throughout. An oven or toaster oven restores a drier skin, while a microwave is faster but leaves the outside soft.
The skin is edible after thorough washing, although you may want to cut away damaged, bitter, or heavily charred sections. Sticky syrup and dark patches on the surface, on the other hand, are normal. However, discard any potato that is moldy, smells fermented, or has turned unusually soft.
Ideas for Safe Leftovers
Slice cold yakiimo as a snack, mash it into a filling, or stir it into soup as a natural thickener. Buying only the size you need, and freezing extras, also cuts waste.
Yakiimo Nutrition
Conveniently, Japan’s official food composition tables include a separate entry for roasted sweet potato. The figures below come from food number 02008, “sweet potato, tuberous root, without skin, baked,” which also lists ishi yakiimo as an alternative name.
| Nutrient | Per 100 g edible portion |
|---|---|
| Energy | 151 kcal |
| Carbohydrate | 39.0 g |
| Dietary fiber | 4.5 g |
| Potassium | 500 mg |
| Vitamin C | 13 mg |
Source: Standard Tables of Food Composition in Japan 2020, Eighth Revised Edition, Supplement 2023. Values are for baked sweet potato without skin. They are not specific to skin-on yakiimo or to any one variety such as Beni Haruka.
As a worked example, a 150 g edible portion would provide an estimated 227 kcal, 58.5 g of carbohydrate, 6.8 g of dietary fiber, 750 mg of potassium, and 20 mg of vitamin C. These are simple calculations from the official values, not separate lab measurements. In practical terms, yakiimo provides dietary fiber, potassium, and some vitamin C, with no added sugar when served plain.
Yakiimo History
Edo Period: The First Yakiimo Sellers
Sweet potatoes reached Ryukyu (today’s Okinawa) in 1605 and then spread north. A chronology compiled by the Kawagoe Imo Tomo no Kai places the first yakiimo seller in Edo, now Tokyo, in 1793. Vendors then roasted the potatoes in pans over a hearth, not on stones. By the early 1800s, when sugar was still expensive, cheap yakiimo had won over rich and poor alike.
Why “Jusanri” Means Yakiimo
Edo sellers advertised yakiimo as jusanri, literally “thirteen ri,” an old unit of distance. Kuri (chestnut) sounds like “nine ri,” so nine plus four made a pun on kuri yori umai, “better than chestnuts.” Some accounts instead link the number to the distance between Edo and Kawagoe, a sweet-potato-growing area.
From Pot-Roasting Shops to Stone-Roasting Carts
Kariya describes four yakiimo booms, the first in the late Edo period. In the second, after the Meiji Restoration, specialty shops appeared in fast-growing Tokyo, and many sold shaved ice in summer. Then, from 1941, wartime food control largely stopped yakiimo sales.
Those controls finally ended in 1950. Then, around 1950 to 1951, stone-roasting carts appeared on Tokyo streets, loaded with an iron box of hot pebbles. However, sources differ on the exact year. Some accounts, for example, credit Manzo Minowa with creating and popularizing cart-based stone roasting in postwar Tokyo. Compared with older pot-roasting methods, stone ovens let vendors roast larger batches on the move.
The Truck and the Call
Stone-roasted yakiimo peaked during Japan’s high-growth years, and for many people the drawn-out call of “ishi yakiimo” from a slow truck still means winter. After the 1970 Osaka Expo, however, fast food spread, and the carts declined. Mobile vendors never vanished completely, but they were never the only way to buy yakiimo either. For a broader look at yatai snacks, see our guide to Japanese street food and festival stalls.
From Winter Street Food to Year-Round Snack
The current boom, by Kariya’s account, began in 2003. That year, electric yakiimo ovens first began appearing in supermarkets, starting with a chain in Shizuoka. As a result, selling moved from trucks to fixed counters. NARO also notes that in-store roasters are now widespread and that demand continues into summer, which chilled and frozen yakiimo now serve.
Where to Buy Yakiimo in Japan
For most visitors, the easiest option is a supermarket, since many roast sweet potatoes in-store during autumn and winter. Specialty shops offer more varieties, and in winter you may still hear a truck. Stock, however, varies by branch and season.
Yakiimo Prices in Japan
Shops price yakiimo per potato, by weight, or in fixed packs, so check which one you are looking at before comparing. For example, oimo lab. lists its yakiimo from ¥300 each on its official website.
Japanese Words to Look For
- 焼き芋 yakiimo
- Roasted sweet potato, the general term
- 石焼き芋 ishi yakiimo
- Stone-roasted sweet potato
- 冷やし焼き芋 hiyashi yakiimo
- Chilled roasted sweet potato
- 冷凍焼き芋 reito yakiimo
- Frozen roasted sweet potato
- べにはるか／紅はるか Beni Haruka
- Moist, very sweet variety
- 安納芋 Anno imo
- Very sticky variety from Tanegashima
- シルクスイート Silk Sweet
- Smooth, moist variety
- ほくほく／しっとり／ねっとり hokuhoku / shittori / nettori
- Fluffy / moist / sticky, the three texture labels
Yakiimo Shops in and near Tokyo
Information checked in September 2026. Seasonal shops often change their opening days, stock, and hours, so please check each official website before visiting.
Choumitsu Yakiimo pukupuku (超蜜やきいもpukupuku)
Kurataya (倉田屋)
oimo lab. Yokohama Azamino
This specialist closed its original Kiyosumi-Shirakawa store in July 2024 and now operates in Azamino, Yokohama. It usually roasts three to five varieties, such as Silk Sweet and Beni Haruka.
Yakiimo vs Other Sweet Potato Snacks
Of all these snacks, yakiimo is the plain, whole roasted version. Hoshiimo, dried sweet potato slices from Ibaraki, are steamed, peeled, sliced, and dried. Daigaku imo is fried and coated in syrup, while imo kenpi uses thin, crispy, sugar-coated strips. Imo yokan shapes mashed sweet potato into a firm confection, and Japanese sweet potato cake adds butter, sugar, and egg.
If you are exploring Tokyo snacks more broadly, senbei rice crackers, ningyo yaki, imagawa yaki, and kaminari okoshi make good next stops.
Final Thoughts
Yakiimo is simple, but the details matter. Choose Beni Haruka for a creamy result or Beni Azuma for a fluffy one, roast it low and slow, and trust the skewer over the timer. In Japan, start at a supermarket roaster, then visit a specialty shop to compare varieties. And if you hear “ishi yakiimo” drifting down a winter street, it is worth following the sound.
Yakiimo FAQ
Cooking Questions
- What is the best temperature to cook yakiimo?
-
About 160°C (320°F) in a home oven works well. The moderate setting heats the potato slowly, so its starch has more time to turn into sugar.
- How long does it take to cook yakiimo?
-
Usually 90 to 120 minutes at 160°C for a medium potato of about 250 g. Thicker roots take longer, so finish when a skewer slides through easily.
- Can I use orange-fleshed sweet potatoes outside Japan?
-
Yes, they make a reasonable substitute. However, orange-fleshed sweet potatoes often roast up wetter and taste different from Japanese satsumaimo. So look for purple-skinned, pale-fleshed varieties at Asian grocery stores if you want a closer match.
Eating and Buying Questions
- Is yakiimo gluten-free?
-
Yes. Plain yakiimo is naturally gluten-free because it is simply roasted sweet potato. If you need to avoid gluten strictly, check toppings, packaged products, and possible cross-contact from shared equipment.
- When is the best season for yakiimo in Japan?
-
Late autumn and winter, when stored and cured roots reach shops. Chilled and frozen yakiimo, however, are sold year-round.
References
Research and Official Data
- NARO (National Agriculture and Food Research Organization) – Selecting a sweet potato storage method to supply tasty yakiimo in September, based on preference surveys (Accessed September 2026)
- NARO (National Agriculture and Food Research Organization) – Seasonal topic: Beniharuka, a refined sweetness (Accessed September 2026)
- Ministry of Education, Culture, Sports, Science and Technology (MEXT) – Proposed new values for the Standard Tables of Food Composition in Japan, including food number 02008, baked sweet potato without skin (PDF) (Accessed September 2026)
- Ministry of Education, Culture, Sports, Science and Technology (MEXT) – Food Composition Database, Standard Tables of Food Composition in Japan 2020, Eighth Revised Edition, Supplement 2023 (Accessed September 2026)
- Chiba Prefectural Agriculture and Forestry Research Center – Research report on short-term storage temperature and the sweetness of roasted Beniharuka (2019) (PDF) (Accessed September 2026)
History and Culture
- Agriculture and Livestock Industries Corporation (ALIC) – Kariya, A. The history of yakiimo booms and their background, Vegetable Information, November 2015 (Accessed September 2026)
- Japan Root and Tuber Crops Development Association – Kawagoe Imo Tomo no Kai (2005). A Small Encyclopedia of Yakiimo, including the Edo yakiimo chronology (PDF) (Accessed September 2026)
- SHUN GATE – Yakiimo, a winter snack with 300 years of history (Accessed September 2026)
- Waraku Web – What does “jusanri” on a yakiimo shop mean? An Edo-period pun (Accessed September 2026)
Cooking and Shops
- Panasonic UP LIFE – How to make authentic yakiimo in a home oven, supervised by Satomi Kenmizaki (Accessed September 2026)
- Choumitsu Yakiimo pukupuku – Official website (Accessed September 2026)
- Shinagawa City – Mottainai promotion shops near Nishi-Oi Station (Accessed September 2026)
- Kurataya – Official website and shop information (Accessed September 2026)
- oimo lab. – Official website and store information (Accessed September 2026)
Related Articles
- Japanese Sweet Potato (Satsumaimo) (Surveyed: September 2026)
- Beniharuka Sweet Potato (紅はるか) (Surveyed: September 2026)
- Anno Imo (安納芋) (Surveyed: September 2026)
- Silk Sweet (シルクスイート) (Surveyed: September 2026)
- Benikomachi Sweet Potato (紅小町) (Surveyed: September 2026)
- Hoshiimo: Japan’s Dried Sweet Potato Snack (Surveyed: September 2026)
- Daigaku Imo (大学芋) (Surveyed: September 2026)
- Japanese Street Food (Surveyed: September 2026)
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