Akira Haraguchi (原口 證 Haraguchi Akira?) (born 1946), a retired Japanese engineer, currently working as a mental health counsellor and business consultant in Mobara City, is known for memorizing and reciting digits of pi.
He claims to hold the current unofficial world record (100,000 digits) in 16 hours, starting at 9 a.m (16:28 GMT) on October 3, 2006 and having recited up to 83,431 digits by nightfall, stopping with digit number 100,000 at 1:28 a.m. on October 4, 2006. The event was filmed in a public hall in Kisarazu, east of Tokyo, where he had five-minute breaks every two hours to eat onigiri to keep up his energy levels. Even his trips to the toilet were filmed to prove that the exercise was legitimate. Haraguchi's previous world record (83,431), was performed from July 1, 2005 to July 2, 2005. On Pi Day, 2015, he claimed to be able to recite 111,700 digits.
Despite Haraguchi's efforts and detailed documentation, the Guinness World Records have not yet accepted any of his records set.
The Guinness-recognized number of remembered digits of π is 70,000 digits, held by Rajveer Meena, a 21-year-old BTech holder from India, at the VIT University, Vellore, India, on 21 March 2015. Rajveer wore a blindfold throughout the entire recall, which took nearly 10 hours.
Earlier, the record was held by Lu Chao. He had recited post decimal Pi values up to 67,890 digits in 24 hours and 7 minutes in 2005.
Haraguchi views the memorization of pi as "the religion of the universe", and as an expression of his lifelong quest for eternal truth.
Haraguchi's mnemonic system
Haraguchi uses a system he developed, which assigns kana symbols to numbers, allowing for the memorization of Pi as a collection of stories. The same system was developed by C.S. Lewis to assign letters from the alphabet to numbers, and creating stories to memorize numbers. This system preceded the system above which Haraguchi developed.
 0 => can be substituted by o, ra, ri, ru, re, ro, wo, on or oh;
1 => can be substituted by a, i, u, e, hi, bi, pi, an, ah, hy, hyan, bya or byan;
The same is done for each number from 2 through 9. His stories are what he used to memorize pi.
- Bellos, Alex (2015-03-13). "He ate all the pi : Japanese man memorises π to 111,700 digits". The Guardian. Retrieved 2015-08-14.
- Otake, Tomoko (2006-12-17). "How can anyone remember 100,000 numbers?". The Japan Times. Retrieved 2007-10-27.