Unagi (鰻, Japanese freshwater eel, Anguilla japonica) is one of the most technically specific preparations in Japanese cooking. A single eel piece in its final glazed form has passed through multiple stages of cooking — splitting, cleaning, skewering, initial grilling, steaming, second grilling, tare glazing — before reaching the plate. This process, called kabayaki (蒲焼), is practiced by specialist unagi restaurants where the cooks train specifically in eel preparation.
Unagi is also a fish with serious ecological concerns — Japanese eel populations have declined dramatically over the past four decades due to overfishing, habitat loss, and disruption of migration routes. The species is listed as Endangered on the IUCN Red List.
The Kabayaki Technique
Kabayaki is the specific preparation that defines Japanese eel cooking:
1. Splitting (Saki): Live eel must be killed quickly at the moment of preparation — the standard technique is a metal spike through the head to pin the eel, then a single cut along the spine to split it open. The eel is simultaneously alive and extremely slippery, requiring skilled technique. Different regional knife positions are used for this split (see Kanto vs Kansai below).
2. Cleaning: The spine, internal organs, and head are removed; the eel is filleted into a bone-free flat piece.
3. Skewering (Kushiuchi): The flat fillet is skewered on several thin bamboo or metal skewers to keep it flat during grilling — eel skin contracts and curls when heated; the skewers prevent this.
4. First Grilling: The skewered fillet is grilled over charcoal (binchotan is traditional; gas grills are now common) — briefly, just enough to cook the surface and render some fat.
5. Steaming (Mushi): The partially grilled eel is placed in a steamer and steamed for several minutes. This step is specific to the Kanto (Tokyo) style — it removes excess fat from the flesh, produces a more tender, almost melting texture. Kansai (Osaka) style omits steaming entirely, going directly from the second grill to glazing. The steamed version is softer; the unsteamed version is firmer and more charred.
6. Second Grilling: After steaming, the eel goes back on the grill. This second pass creates the outer caramelization.
7. Tare Glazing: The key flavor element — unagi tare (鰻のたれ) is a thick, sweet-savory glaze made from soy sauce, mirin, sake, and sugar (and sometimes mirin moromi, sweet sake sediment). The eel is brushed with tare repeatedly during the final grilling — each pass of the glaze caramelizes onto the surface, building up layers.
The tare secret: Famous unagi restaurants maintain tare that has been added to and reduced continuously for decades. The accumulated rendering of thousands of eels into the tare over years produces a depth that fresh tare cannot replicate. Old tare is considered one of the most valuable assets of a long-running unagi restaurant.
Kanto vs Kansai Style
| | Kanto (Tokyo) | Kansai (Osaka) | |---|---|---| | Splitting | From the back (dorsal side) | From the belly (ventral side) | | Steaming | Yes — after first grill | No — skips steaming | | Texture | Softer, melting, less charred | Firmer, more caramelized crust | | Cultural note | Split from back = "not cutting the belly" (merchant's superstition about harakiri) | Different food culture; firmer is preferred |
The split-from-back rule in Kanto has a historical explanation: Edo (now Tokyo) was a city of merchants. Opening the belly (hara wo kiru) evoked harakiri (ritual suicide), an inauspicious image for business culture. Kansai, with different cultural priorities, had no such concern.
The Serving Formats
Unadon (鰻丼, Eel Rice Bowl)
Kabayaki-prepared eel fillet placed over a bowl of white rice, additional tare drizzled over the top, optionally topped with sansho pepper (Japanese pepper, the correct accompanying spice). This is the most accessible and common format.
Unaju (鰻重, Eel Lacquer Box)
The same preparation as unadon but served in a jubako (重箱), a black lacquer box, with the eel placed precisely on top of seasoned rice. The lacquer box indicates a higher price point and more formal presentation.
Grades: Unaju boxes typically come in grades (松, 竹, 梅 — pine, bamboo, plum, from highest to lowest) that indicate the amount of eel per serving.
Hitsumabushi (ひつまぶし) — Nagoya Style
Nagoya's regional unagi specialty — served in an ohitsu (a wooden rice serving tub) rather than a single bowl. The preparation:
- Finely chopped kabayaki eel is mixed into the rice in the ohitsu and served with tare
- Divided into four portions: the first portion is eaten plain as eel and rice; the second is eaten with toppings (green onion, wasabi, nori, etc.); the third is eaten ochazuke-style with green tea or dashi poured over the rice-eel mixture; the fourth is the best version of the three
- The purpose is to experience the same eel preparation in multiple forms in one sitting
Hitsumabushi is Nagoya's most distinctively local food preparation.
The Summer Eel Tradition: Doyo no Ushi no Hi
Doyo no Ushi no Hi (土用の丑の日) — "the Ox Day of the Doyo Period" — is the specific day in midsummer (determined by the traditional Japanese calendar system; typically late July, sometimes twice in the same season) when eating unagi is considered essential for health and stamina.
The origin (disputed): The most common explanation attributes the tradition to the Edo-period scholar and inventor Hiraga Gennai (1728–1780), who was supposedly hired by a struggling eel restaurant and proposed that "ox day of the doyo" — a day associated with foods beginning with "u" in Japanese (based on traditional calendrical beliefs) — should be a designated eel-eating day. Whether this story is accurate or retroactive legend is debated.
The health belief: Unagi has long been associated in Japanese traditional medicine with stamina and recovery from summer fatigue (natsubate, 夏バテ) — the weakness and exhaustion caused by Japan's oppressive humid summer heat. Eel is high in protein, B vitamins, and omega-3 fatty acids; the association is not medically precise but is culturally persistent.
The scale: On Doyo no Ushi no Hi, Japan consumes approximately 70 million eel servings. Convenience stores and supermarkets stock pre-packaged unadon; unagi restaurants run months in advance. It is the single highest sales day in the Japanese eel industry.
Sustainability Concerns
Anguilla japonica (Japanese eel) has experienced a decline of approximately 75–90% in estimated population since the 1970s. The drivers:
- Overfishing of juvenile eels (shirae, glass eels) used to stock aquaculture ponds — unagi cannot currently be farmed from egg to juvenile; all aquaculture depends on wild-caught juveniles
- Loss of river habitat (dam construction, channelization)
- Disruption of migration routes (eels spawn in the Pacific near the Mariana Islands and return to Asian rivers as adults)
- Climate change affecting ocean currents used for migration
Conservation response: Japan has implemented catch quotas on glass eels and adult eels; some restaurants now source eels from outside Japan (European eel, Anguilla anguilla, also endangered, or American eel) or use certified sustainable suppliers. Research into unagi aquaculture from egg-to-adult is ongoing but not yet commercially viable.
Unagi in Japan is not yet a food that requires abstention — licensed sustainable suppliers exist — but it is a food that warrants awareness of sourcing.
Related reading: Sashimi Fish Types Guide | Nagoya Food Guide | Japanese Donburi Types Guide
The full recipes live in the book.
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