Along with Kada no Azumamaro, Motoori Norinaga, and Hirata Atsutane, he was regarded as one of the Four Great Men of Kokugaku, and through his research into the spirit of ancient Japan (through his studies of the Man'yōshū and other works of ancient literature) he expounded on the theory of magokoro, which he held to be fundamental to the history of Japan.

Mabuchi was born in 1697 in the village of Iba in Tōtōmi Province (currently part of the city of Hamamatsu, Shizuoka), as the third son of Okabe Masanobu.

The Okabe were hereditary kannushi of Kamo Shrine in Kyoto, but his father was from a cadet branch of the clan and was a farmer.

In 1707, he began training under Sugiura Kuniakira, a kokugaku scholar with a private academy in Hamamatsu and a disciple of Kada no Azumamaro.

[2] An explanatory marker stands at the site of Mabuchi's residence in Edo (Hisamatsu-cho, Nihonbashi, Chūō, Tokyo), and a memorial museum was built beside the house where he was born in Hamamatsu.