Nida shinda otoko

Naruto thinks back to the time when he encountered the soul of a man named Kisuke. Kisuke didn't recall anything about who he was, but a visit to the Leaf Village's hospital revealed something startling. Meanwhile, higher-ups of the Fire Country met to decide on a new security system for the Leaf Village put together by a ninja named Sabiru. Who exactly were Kisuke and Sabiru, and what connection did the two have?