The New Zealander, who currently works as technical advisor to Japanese league side NEC Green Rockets, arrived in Japan on Wednesday for a meeting with the Japanese Rugby Football Union (JRFU) and is expected to be unveiled at a press conference on Thursday.
The 41-year-old will initially take on the post of technical advisor until the end of the year, when his contract with NEC will expire, leaving him to take over as head coach of the Cherry Blossoms.
Kirwan, for his part, had his Italy contract rescinded in April 2005. He was under contract until 2007 but his position came under scrutiny after the Azzurri failed to win a game in the 2005 Six Nations championship.
"He has a clear vision to win at least two games at the World Cup," said Ota.
"He has a long-term vision to improve the Japan national team.
"He has agreed to live in Japan, he understands Japanese culture and customs, and has previously coached an international team."
Kirwan had a glittering career with the All Blacks, playing 63 Test matches and scoring 35 tries.