Nanjo was born in the United States and began playing chess in elementary school, becoming the 5th Grade U.S.
Elementary School Chess Champion alongside Hikaru Nakamura.
[1] Nanjo has won the Japanese Chess Championship five times, in: 2010, 2012, 2014, 2023, and 2024.
[5][6] As of September 2023, Nanjo is one of two active International Masters in Japan, alongside Shinya Kojima.
[7] In October 2023, he finished second in the Nagoya Open 2023, behind winner Piotr Sabuk.