In the mid-80s, while still working for Tatsunoko, Mashimo survived a severe alpine skiing accident. During his stay in an intensive care unit, he came up with an idea of a "hospital for animators", an animation studio whose primary goal would be fostering and self-actualization of talented artists rather than commercial success and money. Some time after that, he founded a small freelance studio called Mashimo Jimusho that was mainly producing in-between animation for larger companies. In 1997, Mashimo presented his studio-as-hospital concept to Mitsuhisa Ishikawa, the president of Production I.G, who was so impressed with it that he immediately agreed to sponsor Mashimo. The new subsidiary has become known as Bee Train and in February 2006, it ended its relationship with I.G and became independent.
Mashimo is known for frequently hiring Yuki Kajiura to compose for his projects. Their first project being Eat-Man, then going onto Noir, as well as .hack//Sign, Liminality, and Tsubasa Chronicle. Besides Kajiura, many Mashimo and Bee Train's projects bring back seiyūs and crew members. Some noted cast members include: Maaya Sakamoto (Blade of the Immortal, Tsubasa Chronicle), Sanae Kobayashi (Madlax, .hack//Roots, .hack//Liminality), as well as noted crew members such as character designer Minako Shiba, Koji Sawai, and Hiroyuki Kawasaki.
Mashimo's approach to music is to have the music play a key role in the series. He feels music and animation should work and push each other to new heights all the time, and it should be seen as more than simple background.
Some of Mashimo's major projects have featured strong female protagonists. The famous "girls with guns" trilogy (Noir, Madlax, El Cazador de la Bruja) have all featured female characters in lead roles. One of his earlier films, The Weathering Continent, also featured a young woman who takes matters into her own hands to save her people. Some have also been known to contain subtle hints at lesbian relations, most notably in Madlax.
|1975||Time Bokan||assistant director|
|1978||Kagaku Ninja-Tai Gatchaman II||director|
|1979||Kagaku Ninja-Tai Gatchaman F||director|
|1985||Night on the Galactic Railroad||script|
|1987||Dirty Pair: Project Eden||director, general superintendent|
|Dominion: Tank Police||director, script|
|1990||Robin Hood no Daiboken||director|
|1992||The Weathering Continent||director, script|
|1993||The Irresponsible Captain Tylor||director, script, supervisor|
|1998||Xenogears||animation movie producer|
|Wild Arms: Twilight Venom||director, planning|
|2001||Noir||director, storyboard, sound director, music director|
|2002||.hack//Sign||director, script, sound director, soundtrack supervisor|
|.hack OVAs: .hack//Intermezzo, .hack//Unison, .hack//Gift||director|
|.hack//Liminality||director, soundtrack supervision, animation director|
|.hack//Legend of the Twilight||director, general superintendent|
|Immortal Grand Prix||director, script|
|2004||Madlax||director, script, storyboards|
|Ginyuu Mokushiroku Meine Liebe||director, script|
|2005||Tsubasa Chronicle (first season)||director, story boards|
|2006||Ginyuu Mokushiroku Meine Liebe wieder||director|
|.hack//Roots||director, supervision, soundtrack supervision, consulting producer|
|Spider Riders||director, supervision|
|Tsubasa Chronicle (second season)||director (co-director: Hiroshi Morioka)|
|2007||El Cazador de la Bruja||director|
|Spider Riders: Yomigaeru Taiyou||director|
|2008||Blade of the Immortal||director|
|Batman Gotham Knight: Field Test||segment producer|