Sakari Momoi received a certificate from Guinness World Records on Wednesday. He succeeds Alexander Imich of New York, who died in April at the age of 111 years, 164 days.
The world's oldest living person is also Japanese: Misao Okawa, a 116-year-old woman from Osaka.
Momoi was born Feb 5, 1903, in Fukushima prefecture, where he became a teacher. He later moved to the city of Saitama, north of Tokyo, and served as a high school principal there until retirement.
Momoi says he enjoys reading books, especially Chinese poetry. He has five children and now lives at a nursing home in Tokyo.