Denzo Ishizaki was born in Gundo Village (later Kanasagō; present-day Hitachiōta City), Ibaraki Prefecture, Japan, on 2 October 1886.
After graduating from Ota Junior High School (present-day Ota Daiichi High School), he became a teacher at a higher elementary school under the old system. At the young age of 27, he became the principal of the school and served until he was over 40. In 1912, he got married and had four children (two sons and two daughters). In 1946, his wife passed away. After retirement, he lived in his house while farming. He served one term as a village councilor.
Ishizaki started abstaining from alcohol and smoking around the age of 60, and he was never ill, but at the age of 108 he lost his eyesight due to cataracts. He decided to undergo surgery so that he could continue to reading. In his later years, his morning routine consisted of waking up at 3 AM, massaging himself and exercising, doing 80 pressure points, listening to the radio at 5:30, and reading three newspapers after breakfast. At the age of 107, he and his eldest daughter used to travel about an hour by bus and train to museums and art galleries in Mito City, and often visited department stores in Tokyo. He also paid attention to nutritional balance and planned his own daily menu.
Until he fell and injured himself in the early summer of 1997, at the age of 110, he walked 5,000 steps in and around his house every day, and claimed it was one of the secrets of his longevity, along with lukewarm baths, and beef. He also humorously replied: “It’s a secret because it’s called a ‘secret’. Ask God.” As an elderly man, he used to spend at least 5 hours a day reading. He lived with his eldest daughter. Around March 1999, a month before his passing, his physical condition deteriorated and he was recuperating at home.
Ishizaki died from multiple organ failure in his hometown on 29 April 1999, at the age of 112 years.