Sushi 21 (watertown square on mount auburn st.) remains my favorite everyday Japanese restaurant in the area. It is not stuffy or pretentious like so many sushi bars in the area, but is very relaxed and reasonably priced.
Last night I experienced their Bento Box for the first time. I was a little fretful, having been disappointed by bentos at other restaurants but was taken aback by the beautiful presentation and generous serving. What I received were 4 pieces of nigiri, 3 pieces of maki, and several select slices of tuna and yellowtail artfully set in a small wine glass, a generous portion of delightful chicken and beef teriyaki, a very generous amount of fresh and crisp tempura (2 shrimp and several veggies), a gyoza, a shumai, a bowl of rice, and a fresh green salad with delicious sesame dressing. All this for $21 and served by a very accommodating and friendly staff.
Now, I do believe Oishii to be a step up, but that is more of a special occasion place. After several months in this country, my Japanese sister-in-law has finally found a respectable Japanese restaurant. Sushi 21 is quite reminiscent of a neighborhood sushi place in Japan.
For those who cant seem to pull themselves away from New Ginza down the street, please do I did not enjoy my experience there, very stuffy, horrible music, and equally good sushi was about 25% more expensive.