Nairobi is pretty far from the sea and and other fresh water body, and I normally would hesitate to eat raw fish in such a location,
but Misono restaurant nairobi, which has opened in a brand new office/shopping center in Kilimani,
serves good and authentic Japanese food, including respectable sashimi and sushi.
They have bent to box lunch specials, which are a treat, as well as a full range of other dishes (gyoza, udon, katsudon, etc.) as well as teppanyaki.
I haven't tried everything they have, but my lunch was very good, the tempura perfect and both cooked and raw fish excellent.
Lunch cost about Ksh. 1,400 per person, drinking only tea and water.
For the best Sushi in Nairobi, check out Misono. They have relocated to the Greenhouse on Ngong Rd with a bigger and better menu.
Mr Song & his wife are always around making sure you get the best quality food.
They have a delixious avocado sauce and 'special sauce' to accompany your meal giving it that extra edge. Service is ok but we seem to manage given the food.