Hisako Matsui’s “Leonie” depicts the travails of the East Village-raised teacher, editor, and journalist Léonie Gilmour (1873-1933), who has gone down in history as the mother of the sculptor Isamu Noguchi and the Martha Graham dancer Ailes Gilmour.

The costume drama was made in 2009 and released in Japan in 2010. Having been radically recut, the version released in the U.S. this March made only $46,000 at the box office. However, that shouldn’t deter viewers from seeing the movie when it’s released on DVD and simultaneously becomes available for digital download and VOD on May 14.

Although Matsuo’s direction is over-polished and the film wears its feminism on its sleeve, Emily Mortimer gives one of her finest and fiercest performances as the title character, a spiky, sensual intellectual, in whose honor the term “bluestocking” should be retired.

There’s a story of great courage and determination here. If Noguchi’s celebrity was the excuse for the picture, it is exemplary in its focus on a woman who defied the conventions of America’s and Japan’s societies to bring up her children as a single mother.

The recipient of Bryn Mawr’s first four-year college scholarship, Gilmour was unable to complete her degree because of illness and the grant’s expiration. She began teaching in New Jersey and took editing jobs. In 1901, she became the Japanese poet Yone Noguchi’s editor and was instrumental in helping him publish the fictional journal “The American Diary of a Japanese Girl.”

The two became lovers and they conceived Isamu in March 1904, at which point their romance was ending. The outbreak of the Russo-Japanese War demanded of the nationalistic Yone that he return to Japan and he left that August. Gilmour gave birth to Isamu in Los Angeles in November 1904.

Yone partially provided for Gilmour and their 2-year-old son when she followed him to Japan at his request in 1907. But having started a family with a Japanese woman, he made it clear he wasn’t going to live monogamously with Gilmour; in the film, he doesn’t live with her at all, though she continued to edit his work.

Supporting herself as an educator, Gilmour lived a nomadic life in Japan, gave birth to Ailes in 1912 (the father, unknown, was another Japanese man), and built a house in Yokohama. She sent Isamu to be educated in America in 1918, and returned there with Ailes in 1920.

Although Isamu served a brief apprenticeship with the artist and sculptor Gutzon Borglum, the creator the Presidents’ heads at Mount Rushmore, it was his mother who diverted him from pre-med at Columbia to study at the Leonardo da Vinci Art School in New York. The movie doesn’t underplay her early vision that her son’s birthright was to be an artist.

Probably because Katharine Hepburn attended Bryn Mawr, Mortimer channels Hepburn note-perfectly, specifically her voice and angularity. The critic David Thomson partially credits Hepburn’s air of superiority to “a deliberately, if not aggressively, emphasized Bryn Mawr accent” — and that’s Mortimer, too, in “Leonie.”

She does what Daniel Day-Lewis did with John Huston in “There Will Be Blood” (and Jeremy Northam did, less consciously, with Robert Donat in “The Winslow Boy” remake). As Day-Lewis availed himself of Huston’s “Chinatown” robber baron Noah Cross in playing Daniel Plainview, so Mortimer avails herself of Hepburn’s iconic independence and moral force — as the aviatrix Cynthia Darrington in “Christopher Strong,” as the missionary Rose Sayer in Huston’s “The African Queen,” in all those battles of the sexes with Spencer Tracy.

“As a child I watched Spencer Tracy-Katharine Hepburn movies without really knowing what they were, but loving them,” Mortimer told Salon last year. In “Leonie,” she not only makes us think of Hepburn’s back catalogue of invincible women, but of Hepburn’s long relationship with the married Tracy, in which she is said to have mothered him.

Gilmour’s possibly thankless devotion to Noguchi’s writing contains elements of that. Her passionate, selfless maternalism may be at odds with Hepburn’s ambitiousness, which precluded childbearing, but both made sacrifices for art. Gilmour was both stoic and maverick, a heroine ahead of her time, who now lives and breathes through Mortimer’s belief in her.