Unagi, or freshwater eel, is so popular a dish in Japan that stocks are in serious decline. On the other hand anago – the more subtly flavoured saltwater eel – is rarely seen on Tokyo menus. The rich flavour of unagi comes from its oily skin and flesh, but anago (conger eels) are leaner, and have a softer, lighter taste. There is, according to chef Yuji Sato, only one restaurant specialising in anago left in the capital, and it’s his.

Tamai opened 10 years ago, on the premises of a former sake merchant in the Nihonbashi business district, and its timber-framed building, dwarfed by high-rise office blocks, is itself a taste of times gone by. Sitting in simple wooden booths, customers can order anything they like – so long as it’s eel.

The signature dish is hako-meshi (about £14): anago grilled or poached and served on a bed of rice in a lacquer box, with condiments and miso. It comes with a little grater and brush for spreading yuzu (citrus fruit) juice and zest over the fish. When you’ve finished eating the eel, a waiter arrives with an individual kettle of eel stock – the very water your fish was cooked in – to pour over the remaining rice and create a rich broth.

Beer comes frothy in ceramic cups, or there’s lemon or plum shochu sour; either goes incredibly well with the starter of fried eel bones, crispy (and high-calcium) snacks that look like they’re made of Lego. The anago tempura is also excellent, so it’s no wonder this place has a long queue every lunchtime. An evening reservation is the best bet, although the staff often want to close up around 9pm, so service may get brisk as the evening wears on.
• +81 3 6228 3103, anago-tamai.com