A mere couple of years ago Yosaku was unique as an uptown sushi bar. Now it is in the midst of plenty, but it remains unique in the breadth of its fish appetizers. In addition to the usual sushi, expertly done and served efficiently in a very Japanese-looking dining room, Yosaku offers interesting seasonal dishes, more on the weekends than on weekdays though. We missed skewered pork and vegetables, and lobster on a weeknight, but there still was a luscious and enormous yellowtail cheek -- the sweetest meat of the fish-grilled so the skin crackled and the flesh as soft and juicy. An inexpensive appetizer, it was as large as most main dishes. The menu also listed salmon cheek, softshell crabs, thinly sliced flounder and slightly grilled chunks of tuna amng its appetizers. Or you can have raw beef instead of fish. There are also several marinated seafood salads, cold vegetables such as spinach with a nutty sauce and bean curd boiled, chilled or fried. Main dishes are not the exciting part of this menu -- the tempura is generous but slightly doughy; teriyaki chicken looks like diner food and doesn't taste much better. Yosaku is to be enjoyed for its variety of fish dishes at decent enough prices that sushi can be everyday fare. And check the sign in front for occasional specials such as all- you-can-eat sushi, which make the value even better. 4712 Wisconsin Ave. NW. 363- 4453. L $4-$7, D $7-$11.50. L daily ex Sat, Sun, D daily. AE, MC, V. No res. Full bar.