SHIROYA -- 2507 Pennsylvania Ave. NW. 659-9449. Open: for lunch Monday through Friday 11:30 a.m. to 2 p.m.; for dinner 5:30 to 10:30 p.m., Saturday 3 to 11 p.m., Sunday 5 to 10 p.m. All major credit cards. Reservations suggested. Separate non-smoking section. Prices: lunch appetizers $2.50 to $5, entrees $6.50 to $10.50; dinner appetizers $2.50 to $6.50, entrees $8.50 to $20. Full meal with beer, tax and tip about $20 to $25 per person.

In its original location, Shiroya was a run-of-the-mill Japanese restaurant in a handsome modern environment. Now that it has moved down the street, it is in a run-of-the-mill environment -- just one of those ever-changing restaurants in the West End along Pennsylvania Avenue. And the food is pretty much what you would find in a dozen or more of the city's Japanese restaurants. But somehow the ordinary parts of Shiroya add up to something unique.

First, I can't think of any other Japanese restaurant with a sidewalk cafe' (it's a delight to eat sushi under the stars). Second, Shiroya seems utterly Japanese, the first indication being the glass case of plastic food models so common in the windows of Tokyo's restaurants.

The waitresses wear kimonos with aprons over them, and the sushi chefs are likely to be wearing jeans. What could be more Japanese? The outdoor terrace, tucked under a canopy and closed in by a low wooden wall, is a structure of Japanese style. And inside, the small space has been carved into distinct parts in an efficient and most attractive arrangement. A very Japanese use of space.

Shiroya is not only pretty, it is also comfortable. Gentle Japanese music plays in the dining room. The spare, boxy chairs are upholstered. The tables are well spaced for such a small area. The walls and room dividers are like Japanese shoji screens, their translucent panels framed by wood strips, and softly lit by hanging lamps with woven shades. And on the tables are tiny pottery soy sauce pitchers and cute covered porcelain toothpick holders.

Dinner begins with damp washcloths and perhaps sake or Japanese beer from the large selection. While the menu is standard for local Japanese restaurants -- sushi, sashimi, tempura, teriyaki, negimaki, tonkatsu, yosenabe and sukiyaki -- it is presented in thoughtful combinations. You can order just a bit of sushi or a full meal of it with very good miso soup, a tiny sweet-vinegared cucumber-seafood salad and a charming dessert of sliced oranges arranged in their skin. Other entrees can be ordered a la carte or, for just a dollar or two more, as a complete meal with soup, green salad with horseradish dressing, rice and dessert. And there is a deluxe combination dinner with three entrees. My favorite combinations, though, are the lunch and dinner boxes (lunch is a particular bargain). After soup and salad comes a lacquered box, its compartments filled with tempura, sashimi, sweetened steamed egg, bits of super-salty pickles, rice and an enormous portion of chewy but well-seasoned, soy-marinated, paper-thin beef. All this for $7.50. The dinner box, which includes more entree samples and dessert, is $18.

It is good food, not stellar. One day the tempura was excellent, light and crisp batter with no greasiness. Another day it was heavier. In any case, it features the usual ingredients -- a shrimp, a slice of chicken breast, hunks of eggplant, green pepper, sweet potato, onion and broccoli. The sushi selection, too, is ordinary, with no belly tuna, salmon skin, sweet shrimp or exotic specialties. But it is good, fresh fish, the yellowtail soft and buttery, the eel deliciously unctuous, the sea urchin delicately sweet and the flounder clean-tasting. Not fancy, just good.

Grilled foods are less good. Beef teriyaki is mushy, probably from being pounded with a tenderizer. Negimaki, thinly sliced beef rolled around scallions, is dry. And cooked seafood appetizers -- soft-shell crabs and shishamo (smelts) -- have tasted fishy and greasy. A couple of other appetizers have been better. Small skewers of yakitori are pleasant, and cold spinach under a fluff of shaved bonito, ginger, scallions and sesame seeds is refreshing. Appetizers also include chilled, fried or boiled bean curd, which is handsomely presented in a covered bowl with sauce in the center. In most cases, though, the dinner accompaniments of soup and salad make a la carte appetizers irrelevant, just as the complimentary dessert of sliced oranges forestalls interest in other desserts -- ice creams, fruits and sweet bean paste.

I'm a sushi fan. And I find it hard to turn my attention from sushi, sashimi or the lunch-box combination to cooked entrees. Still, one has been outstanding. Yosenabe -- a tureen of fish and seafood chunks, abalone slices, a shrimp and clam or two and diced chicken in broth -- is aromatic and as satisfying as mom's chicken soup, not to mention luxurious. It is just right for a slightly chilly evening outdoors or in, and it is plentiful enough to share (oddly, you can order it as a complete dinner for one, but a la carte only for two or more).

Yosenabe also illustrates the most pressing problem at Shiroya: insufficient dining room staff. Two very gracious waitresses race around trying to satisfy everyone, and in so doing they disappear to other rooms for long periods. When we ordered yosenabe, our harried waitress dropped off our entrees and rushed off. So there we sat, our table filled with dishes and nowhere to put the heavy metal lid from the yosenabe pot, which was too hot to lift without a potholder anyway. It took at least 10 minutes to flag a waitress to remove the lid, and longer to cadge another spoon so we could share. Other times we have sat through a substantial portion of the background music tape before we managed to get our bill. The staff's graciousness becomes irrelevant when the work load is impossible.

In the wake of the Japanese food frenzy, Shiroya has nothing particularly new to offer. It is not even a new restaurant, just a relocated one. It is simply a comfortable and competent traditional Japanese restaurant offering nothing beyond the standards. But it reminds us why Japanese food became so popular in the first place. ::