[10] One day when he was 14 years old, his father found him sleeping under the porch of the house and severely beat him with a clothes pole, so he ran away from home.

[6] After running away from home, Mikuni hid in the hold of a ship docked in Shimoda, Shizuoka and crossed over to Qingdao, China (then under Japanese control).

[11] He fled with his girlfriend to Karatsu, Saga, and was thinking of crossing the ocean to the continent when he was arrested by Special Higher Police.

[6] He made his debut as the lead role of a newspaper reporter in the film The Good Fairy, directed by Keisuke Kinoshita.

[7][19] At the time of his debut, Mikuni's career was falsified and he was advertised as an intellectual and single male with a degree in engineering from Osaka University.

[22][23] It is said that a sign saying "Do not enter the dog, cat, or Mikuni" was attached to the gate of the Shochiku Ōfuna Studio in Kamakura.

[9] After that, Mikuni appeared in a number of films in both leading and supporting roles, and won numerous awards and honors.

In 1960, he won the Blue Ribbon Award for Best Actor for his role in The Great Journey (大いなる旅路), which chronicled the life of a Japanese National Railways engineer and his family over a thirty-year period.

[25][26] In 1965, he won Mainichi Film Awards for Best Actor for A Fugitive from the Past, in which he played a man who commits a series of murders amidst extreme poverty.

[27] In 1979, he won the Blue Ribbon Award for Best Supporting Actor for his portrayal of a devout Christian man who is the father of a serial killer in Vengeance is Mine.

[28] He became the first individual actor to win three Blue Ribbon Awards, and was called one of the most talented movie stars of the Shōwa era.

[29] The Tsuribaka nisshi series began in 1988, The humorous interaction between Su-san, the company president played by Mikuni, and Hama-chan, a useless employee played by Toshiyuki Nishida, gained national popularity, and the series continued until the 22nd film, Tsuribaka Nisshi 20: Final, released in 2009.

In 1963, he established Nippon Productions and shot Typhoon (台風) as his first independent film, but it was not released due to opposition from Toei, with whom he had an exclusive contract at the time.

and in 1972 he produced, wrote, directed, and starred in River Without a Shore (岸辺なき河), which was shot in the deserts of Pakistan and Afghanistan, but was not completed.

He received Medal with Purple Ribbon in recognition of his outstanding achievements in the field of art and culture in 1984,[9] Order of the Rising Sun, Gold Rays with Rosette (4th class) in 1993.

[37] Yoshio Shirai, a film critic and former editor-in-chief of Kinema Junpo, cited that Mikuni had prepared in his roles so thoroughly that he sometimes tended to overact, and needed a director who could control this well.

In Kon Ichikawa's The Burmese Harp, Mikuni's overacting was truncated in order to make the most of his natural acting.

In Miyoji Ieki's Stepbrothers, Mikuni's preparation in his role was tremendous, but he analyzes that the director is a man with a strong policy, so he made excellent use of his unusual emotions as an actor.

On the other hand, he says that the range of Mikuni's acting ability is overwhelming when looking at his droll performance seen in the Tsuribaka Nisshi series.

[40] He disliked being tied down to one woman and left her as soon as he lost his passion for her, because it would narrow his horizons and interfere with his work as an actor.

He was older than her parents, and her grandmother, who knew of his history of his love affairs, was vehemently opposed to the marriage, but he lived with her until the end of his life.

He loved this place where he could see Suruga Bay and Mount Fuji, and spent his later years walking and tending to his garden.