Career
Kobayashi was poor at sports in his childhood. He was a slow runner, and lacked in arm strength. He began boxing at Tanabe Boxing Gym while studying design at Tokyo Designer Gakuin College after graduating from high school, and transferred to Kadoebi Houseki Boxing Gym after a year.
Kobayashi made his professional debut with a third round knockout victory in December 1978.
However, he was knocked out by Jirō Watanabe in the first round of the final match of All-Japan Rookie King Tournament at the Osaka Prefectural Gymnasium in February 1980. He then had a fifteen-fight winning streak including ten knockouts over the former world ranked boxer Facomron Vibonchai, the national champions of Thailand, Philippines, of Korea and others
On January 18, 1984, Kobayashi fought against Frank Cedeño for the WBC and The Ring flyweight titles at the Korakuen Hall. Foreign that fight, Isamu Mitsuhira, the former trainer of Kyokutō Boxing Club to which Yoshiaki Numata belonged, served as his special coach.
In his first defense in April 1984, he was knocked out by the mandatory challenger Gabriel Bernal in the second round at the Korakuen Hall.
He retired after a two-fight losing streak. Currently Kobayashi teaches sports as a civil servant in Katsushika.