Since junior high school, Kobayashi had excelled in English and had vague aspirations of becoming a writer in the future.

Therefore, he was still open for admission after that notice and thought, "If I am going to be a writer, I might as well learn how others live," and with a light heart he entered the theater department of Nihon University's College of Art.

After graduating from college, Kobayashi joined the theater company Izumi-za and worked as a stage actor.

Later, Kobayashi was invited by Banjiro Uemura, president of the dubbing production company Tohokushinsha Film, who said, "You are an actor, aren't you?

After that, his translation work gradually declined, and when Izumiza dissolved spontaneously around 1971, he concentrated on his voice acting career.

Kobayashi had his own particular preoccupations and aesthetics regarding his work, such as "not using a microphone pop filter" and "eating a piece of caramel before recording".

When Coburn died, he commented, "He had gained a new charm in his old age and thought he would be even more successful as an actor...., I have a strange, unsettled feeling, as if a member of my immediate family had passed away.".

[3] Kobayashi played the role of Daisuke Jigen in the anime series Lupin the Third for more than 50 years, from the pilot version in 1969 to the first episode of Part 6 in 2021.

According to the author, Monkey Punch, the model for Jigen's character was James Coburn, who appeared in the movie The Magnificent Seven.

He has also been told by those around him that he "looks like Jigen himself," even when he is not consciously aware of it, to which he expressed his delight, saying, "It's a gratifying story for an actor to hear".

[5] In the fall of 2021, Kobayashi decided to leave his beloved Jigen, citing the 50th anniversary of the anime series broadcast and his advanced age.

He was replaced by Akio Otsuka, known for dubbing Denzel Washington and acting Solid Snake in the Metal Gear series, and whose father is Chikao Ohtsuka, who once played Goemon.