I lived in Tokyo for five years. For sashimi (not a sushi fan), I think Taka is quite fresh, and the quality is high. If you can get sat by Maru San (request at the time of your reservation), he can tell you what is good, fresh, and worth trying.
I've enjoyed very fresh and well prepared seafood at Oceanaire. Once we walked in without reservations around 6:00 pm on a Friday without a problem getting a table, but the place was packed by the time we left. So reservations would be a good idea.