Soichiro Honda was the riding mechanic in the winning car (driven by Shinichi Sakakibara) in the Fifth Japan Motor Car Championship in November, 1924.
The son of a blacksmith, Honda left school at age 15 to work for Tokyo Art Shokai. The company was involved with "manufacture and repair of automobiles, motorcycles and gasoline engines".
The car was powered by a 90 HP, 8.2 liter OX-5 engine from a Curtis "Jenny" biplane. The car is on display in the Honda Collection Hall museum in Japan.
Soichiro Honda was involved in racing until 1936 when he and his brother, Benjiro, were involved in a terrible accident. Soichiro was driving and was thrown from the car in a rollover. Benjiro was seriously injured. He raced one more time before retiring.
Honda went on to build motorcycles and automobiles under the family name.
Additional information and photos are here.