In 1988, Mitani Yuki wrote his first TV series "Still Like Cats" and also wrote a special episode.

In 1991, he wrote the comedy "12 Gentle Japanese" and won the Japan Screenplay Award. In 1993, he wrote the medical drama "Looking Back to See Him Again" co-directed by Setsuro Iwamatsu, Keita Kono, and Takao Kinoshita, which co-starred Yuji Oda and Ken Ishiguro.

In 1994, he wrote the mystery drama "Furuhata Shinsaburo" starring Tamura Masakazu and Nishimura Masahiko. In 1995, he wrote the inspirational film "Miracle Restaurant", which was based on a restaurant facing a business crisis. In March 1996, he wrote the mystery drama "Furuhata Rensaburo 2".

In 1997, Mitani Yuki directed the political-themed TV drama "Don't Call Me Prime Minister." In November, he directed and directed the comedy film "The Big Belly" co-starring Toruaki Karasawa and Kunie Tanaka, which won the Don Quixote Award - Special Mention at the 48th Berlin International Film Festival.

In 1999, he wrote the mystery drama "Furuhata Rensaburo Season 3". In 2000, he wrote the musical stage play "OKEPI" and the detective suspense drama "The Courage of the Right Words". In 2001, he directed the comedy "Everyone's Home", which was set in affluent life, and was nominated for Best Director and Best Screenplay at the 25th Japan Film Academy Awards.

In 2002, he wrote the romantic comedy "Sakamoto Ryoma, His Wife and Her Lover" and was nominated for Best Screenplay at the 26th Japan Film Academy Awards.

In 2004, he wrote the comedy film "The University of Laughter" co-starring Yakusho Koji and Inagaki Goro. In the same year, he wrote the Taiga drama "Shinsengumi" co-directed by Shimizu Kazuhiko and Iseta Masaya, which co-starred Katori Shingo and Fujiwara Ryuya.

In 2006, he directed his third film, the comedy "Hotel with Sky", starring Koji Yakusho and Takako Matsu.

In 2008, Mitani Yuki filmed the comedy film "Magic Hour" co-starring Sato Hiroshi and Tsumabuki Satoshi. The film was nominated for Best Film at the 32nd Japan Film Academy Awards.

At the end of 2009, he wrote the family film "The History of My Family" for Fuji TV Taiqing. In the spring of 2010, he participated in the 20th anniversary spring special of Wonderful Stories of the World.

In October 2011, he directed the comedy film "The Great Undead" co-starring Eri Fukatsu and Toshiyuki Nishida, and was nominated for Best Director and Best Screenplay at the 35th Japan Film Academy Awards. In November, he directed the comedy "Short Sections of Life", which consisted of only one shot.

In November 2013, he directed the historical film "Kyosu Conference" set in Japan's Warring States Period. The film starred Yakusho Koji and Oizumi Hiroshi and won the 37th Japan Film Academy Award for Best Film. Nominated for director and best screenplay. In December, he directed the comedy film "Grand Airport 2013", which focuses on airport worker Chigusa Okawachi.

In 2014, he wrote the mystery and suspense film "Murder on the Orient Express" directed by Keita Kono.

In October 2015, Mitani Yuuki wrote and directed the seventh film "Galaxy Street". The film is set in the universe of 2265 and co-stars Katori Shingo and Ayase Haruka.