My husband and I were happy to discover Blue Fin in the Porter Square exchange. The place is nothing stylish or highly decorated, but it serves very good and honest sushi, the service is fairly quick, and the prices are reasonable for sushi. You always know you came to the right place if a lot of the other customers are Japanese.
The small downside is that on popular nights there can be a bit of a wait, and I don't think they take reservations. But with just 2-3 people, I've never had to wait long anyway.
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