Sorry to disappoint, but there are no Benihana Restaurants aboard NCL ships. But there are Teppanyaki tables aboard NCL ships, which provide a similar experience like Benihana. You'll find the Teppanyaki tables aboard all NCL ships located within the Asian restaurant, except the Majesty, Dream, and Pride of Aloha.
The Spirit only has one Teppanyaki table able to seat approximmately 12, the rest have two Teppanyaki tables. Reservations are required, and there is a surcharge. Book your reservations as soon as you embark the ship, as the limited seats at the limited number of tables go fast.