First things first: the wharf's not part of Dejima; the land didn't even exist during those times. Still, Dejima Wharf is a picturesque harbour-side collection of indoor-outdoor restaurants (serving everything from seafood to Italian at a variety of price points), plus bars and galleries. Add sunset views over the bay – maybe with your sweetie – and it's well worth a visit.
Dejima Wharf
Nagasaki