[2] Jyonai began competing in Super GT in 1997 with the SigmaTec Racing Team.

As of 2023, he has won two races;[2] his best finish in the championship is 5th, achieved in his first year in the series.

Outside of racing, Jyonai is the CEO and President of Marusho Co. Ltd., a company involved in the lighting, security and construction sectors.

[3] He is also a lecturer at the karting classes of Honda Racing School Suzuka as well as a color commentator for various television programs.

[citation needed] He occasionally competes using the pseudonym Guts Jyonai (Guts城内, Gattsu Jōnai);[2] Jyonai says he took the name from comedian Guts Ishimatsu.