In an attempt to add his own character to his movies, his directorial approach follows a "one scene = one shot" system, whereby he pans the camera around as opposed to cutting.

[2] Throughout his life, he has expressed interest in works starring famous detectives, such as the Sherlock Holmes series.

[3][4] He has collected numerous novel volumes, pastiches, and DVDs related to Sherlock Holmes, and in 2014 adapted the story into a puppetry set in a boarding school.

[3] Mitani has also stated that he enjoys foreign cinema, and is a fan of the films 12 Angry Men, The Wages of Fear, Columbo, and the director Billy Wilder.

Mitani is the author of a weekly column in the Asahi Shimbun daily newspaper[1] in which he often discusses his favorite films, his writing process, and the actors and actresses with whom he has worked.