Mr Yukichi Chuganji celebrated his 113th birthday as the world's oldest living man.
The retired silkworm breeder is bedridden and lives with his 72-year-old daughter Kyoko in the Japanese city of Ogori.
His daughter says he eats moderately, enjoying beef and pork with meals of rice and miso soup, and has "an optimistic way of thinking".
"I'm so happy you are celebrating for me," Ms Kyoko Chuganji quoted her father as telling relatives at his home.
Mr Chuganji inherited the title of world's oldest man on January 4 after the death of Italian Mr Antonio Todde just shy of his 113th birthday, according to Guinness World Records.
Mr Chuganji was born on March 23, 1889 in the farming town of Chikushino in Fukuoka state on Japan's main island of Kyushu.
He worked as a silkworm breeder after graduating from technical school as a teenager in the early 1900s.
Earlier this week, Guinness World Records honoured another Kyushu resident, 114-year-old Kamato Hongo, as the world's oldest woman and also as the world's oldest person.
There are an estimated 15,000 Japanese over the age of 100, and women make up about 80 percent of the total.
Japan has the world's longest life expectancy at 79.9 years. The country's traditional fish-based, low-fat diet may be the secret to the long lives, researchers say.
PA