He was too polite to say it was high time that I did, for there is no doubt that Japanese food has arrived. Not long ago, a Japanese meal was an expensive rarity - a trip to Suntory in St James's or the Hilton in Kensington. Now you can buy sushi for pounds 1.50 in Piccadilly Circus Underground station. Above ground in Sogo, the spanking new Japanese-owned department store, it appears on the menu of the cafe, along with Black Forest gateaux.
Fumiya mentioned that even the best restaurants often had inexpensive set lunches, and suggested we meet at Miyama, 38 Clarges Street, London W1 (071-499 2443), near his office in Berkeley Square.
Like many Japanese, Fumiya has long been familiar with Western food. It even infiltrated his family table at home in Osaka. One brother preferred Western breakfasts of Kellogg's cornflakes and orange juice. The other liked the traditional Japanese breakfast of grilled fish and miso soup. His mother used to pick from each.
Miyama, he explained, was not an authentically Japanese restaurant: this is impossible in London. In Tokyo, they would have speciality restaurants - sushi bars, eel bars, noodle bars, chicken grills and so on. By necessity here, single kitchens cater for most styles of food. Hence a variety of menus arrived, an A4 photocopied one exclusively in Japanese characters. I only noticed that I was holding it the wrong way when I saw Fumiya read his horizontally.
The sushi chef at Miyama is very good, said Fumiya; the fish is fresh and cut beautifully so as not to 'damage any of the cells'. Best for this is a ceramic, not steel, knife. Good fish chefs are rare, he added, and, like their Western counterparts, can be arrogant.
From the bilingual menus we settled on the sashimi one (raw fish), pounds 13, a tempura (fried) dish and several dishes from Fumiya's inscrutable photocopy. They were quite delicious: a small roll of blanched spinach with sesame seeds with a slightly fishy dressing. A small tofu 'roast', about half the size of a Mars Bar, came sizzling hot, the coat topped with finely julienned spring onions and seasoned with teriyaki sauce.
Of these palate-ticklers, most interesting to me was a simple dish of green beans. The Japanese eat most things lightly cooked, but these were well cooked to eke out that gutsy, earthy flavour, then spiced again with a slightly fishy sauce.
I studied Fumiya as he dealt with the next course, prising the lid off a red cup. On top of the lid were finely minced fresh ginger and a lump of wasabi, that hot green horseradish puree. Inside were moist buckwheat noodles. He appeared to manoeuvre the ginger and wasabi into the noodles with his chopsticks. I followed suit. As my eyes watered and nose ran, I realised Fumiya had avoided taking much of the wasabi. I had heard somewhere it was a mortal insult to blow one's nose at a Japanese table. I fled to the lavatory.
The sashimi was a revelation. Unlike sushi, which involves various toppings on rice, sashimi is trimmed and cut raw fish with a garnish of cooling, julienned radish called mooli or daikon, lemon, wasabi and a dish of light soy sauce. Here it was tuna, salmon, yellow tail and turbot, the latter pressed like butterfly wings around the lemon wedge.
Studying Fumiya, I learnt that wasabi is not spread directly on the fish, but mixed sparingly with the soy sauce, into which the fish is then dipped. The different meats were cool, rich and savoury; I had never so fully registered their entirely individual tastes.
Fumiya had tempura - fried carrots, beans and prawns accompanied by a light sauce of water, rice wine and fish essence to which he added some chopped ginger. The vegetables were crisp, nearly raw, beneath their great puffs of fried batter. For dessert, we were brought a dish of ripe cherries. The cost, including mineral water, tea, VAT and service was pounds 19 each.
If Miyama was polite, Wagamama, 4 Streatham Street, London WC1 (071-323 9223) was exhilarating. Loosely translated, the name means 'greedy': certainly it is the only place in town where 20 chopstick-wielding Londoners sit at refectory tables devouring noodles from oversized bowls.
It is a ramen restaurant, a Japanese spin on Chinese peasant dishes of noodle soups, enhanced by various ingredients. 'In Tokyo,' says Fumiya, 'it is a meal for a student, or anyone.' In London, it attracts students and young office workers.
The restaurant, designed by the minimalist architect John Pawson, is lean and bright like a sleek school canteen. It is very health-conscious. Cigarettes are put out at the entrance before descending into the basement dining room. Hip young waiters directed us to our seats. Our order was pressed into a small computerised calculator which transmitted it to the kitchen. 'These machines are very popular in Tokyo,' said Fumiya. They're fun here, too.
There was beer and wine, but the most popular tipple was a 'raw' drink, consisting mostly of liquefied carrot and, at a guess, courgettes. This sort of thing, Fumiya surmised, came to Japan from California. He ordered us a selection of dishes - in English. Only one of the staff appeared to be Japanese.
Hiyashi chuka means cool Chinese in Japanese, and it is delicious. Cold noodles came with a bit of soup, roast chicken, sliced cucumber, sliced carrots and a good dab of what seemed like Colman's mustard. 'It could be Japanese mustard,' said Fumiya, 'but the Japanese like Colman's'
Dumplings, I expect filled with minced pork, were perfect - slippery and fresh, with a soy dipping sauce. Spare rib ramen was a huge pot of what tasted like chicken noodle soup, with a plate of tough ribs that arrived 25 minutes later. The bill was pounds 9 each; a light lunch could cost pounds 5.
It was on to a grittier and more authentic setting for the next meal. The basement of the Japan Centre, 66-68 Brewer Street, London W1 (071-439 8035) is a grocery shop-cum-bookstore-cum-caff. Orders were placed at the till and meals were eaten at a dark, hot luncheon counter. Westerners should refer to the colour snapshots of dishes; luckily, the cashier is patient. A robust lunch of, say, grilled eel on rice in Size A costs pounds 3.80; Size B pounds 5.80.
Fumiya had said that Friday night at Arisugawa, 20 Percy Street, London W1 (071-636 8913) would be a festive business. He was not wrong. I was one of two Westerners in the restaurant, and one of the few female guests in a sea of businessmen. To the left of the entrance, a large party sat cross-legged on a tatami mat in a private room. Single diners sat at stools on a long bar. To the right was a network of tables where the diners' legs disappeared through a false floor, and where the waitresses tended tables kneeling and shoeless.
Bell's whisky was flowing freely. A raffle was being held. I won a beer mug and some rice crackers; Fumiya won a bottle of sake. Finally, to much commotion, a table of revellers won the top prize, a trip to Paris. Lovely waitresses worked this funhouse in traditional kimonos, always composed and cheerful.
Fumiya ordered fermented tofu soup, topped with a raw egg that cooks only slightly from the heat of the stock. I was intrigued by this bland, slippery dish, but could not negotiate it with chopsticks. A set chicken dinner was pounds 20; expect to spend pounds 30 all in.
At each meeting, Fumiya presented me with a small gift. Tofu mix. Bonito flakes. Finally, a little guide to London's Japanese restaurants and shops, The Red Directory (Cross Media, pounds 5).