A vivid portrait of a legendary kabuki actor over the course of his career, “Kokuho” joins a rich tradition of films that depict the personal cost of making art. Too often, such stories present an overly simplified version of the given artform’s rigors and qualities, diluting any undergirding sense of what drives the characters to put themselves through the ringer. By contrast, Japanese director Lee Sang-il’s surprise hit “Kokuho” spends a great deal of its lengthy runtime capturing the beautiful physicality and anguished storylines around which the performances revolve, mirroring the many struggles and complicated triumphs of its central protagonist’s existence.

The title “Kokuho” translates to “national treasure,” a title bestowed by the Japanese government upon high masters of an art or craft. Its director, Lee, is best known for his films “Hula Girls” (2006) and “Unforgiven,” a 2013 remake of the Clint Eastwood movie, starring Ken Watanabe. “Kokuho” has become a veritable phenomenon in Japan, where it has earned nearly $100 million since opening in June, shortly after it premiered in Directors’ Fortnight at Cannes. The film was subsequently picked to represent Japan at the Oscars.

After Kikuo (played by Ryo Yoshizawa as an adult and Ryusei Yokohama as a child) — the 14-year-old son of a yakuza leader in 1964 Nagasaki — witnesses the death of his father, he moves to Osaka to begin studying as an apprentice to Hanjiro (Ken Watanabe), widely considered the best kabuki actor in the city. There, he forms a bond with the performer’s son, Shunsuke (Ryusei Yokohama), who only possesses a modicum of passion compared to the intense drive and natural ability to inhabit the role of an onnagata (a man playing a woman’s role in traditional kabuki), beginning a friendship and rivalry that will last for many years.

At nearly three hours, “Kokuho” takes its time in covering the events of 50 years — ending, after its longest of many time jumps, in 2014 — but it remains engaging throughout, in no small part because of its ambivalent perspective toward its protagonist. As viewed by Lee and screenwriter Satoko Okudera (who adapted the novel by Shuichi Yoshida, whose work inspired Lee’s 2010 film “Villain”), Kikuo is deliberately something of a cipher, clearly a performer who takes great pride in his work but whose sense of self and his ability to relate to others is often murky. As becomes clear through the course of the film, kabuki puts high importance on family lineage. Shunsuke is the heir to the House of Tanban-ya to which Hanjiro belongs. Despite his gift, Kikuo must resort to questionable tactics to maintain his standing in the insular community.

When Ryo Yoshizawa takes over the role of Kikuo approximately 40 minutes in, this aspect of his character becomes even more paramount to the essential mystery of “Kokuho.” When not in the heavy stage makeup that blurs the lines between Kikuo and Shunsuke, there is a slight coldness to his affect, especially compared to Yokohama’s more extroverted performance, which constantly calls into question the sincerity of his sentiments. Though other characters bear the extreme strain of kabuki training and performance much more harshly, the 31-year-old actor appears oddly alien as he ages, a man who never fit into the preestablished traditions of his artform who nevertheless achieves success.

In many ways, Kikuo acts as an embodiment of his art’s place in post-war Japan. Though the film makes little mention of the world outside kabuki — save for Kikuo’s mention that the “A-bomb disease” killed most of his family — it subtly forms a portrait of the changing times, signaled primarily by costume and production design. Kabuki never loses its popularity in the film, similar to its continued place of honor in real life, but there’s a great tension between its 17th-century roots and the machinations of the 20th century, reflected most prominently in the Mitsutomo Corporation’s heavy sponsorship of the House of Tanban-ya. After all, it is an elaborate production, which must be bankrolled through distinctly modern means.

To bring all this to life, Lee Sang-il relies heavily on both tight closeups and widescreen long shots that work in tandem to capture the physicality of the many performances. Cinematographer Sofian El Fani (“Blue Is the Warmest Color”)’s bright colors render Yohei Taneda’s art direction and Kumiko Ogawa’s costumes with the appropriate vibrancy. But perhaps the most fascinating touch of all comes courtesy of chyrons that appear when a new kabuki play is introduced. In the American release of “Kokuho,” the Japanese name of the play appears, along with its English translation and a brief description of the play’s narrative. Though performances are not presented in their entirety, this approach offers Western audiences a fuller understanding of the often tragic nature of these tales of unrequited love and death, plus a deeper appreciation of kabuki’s legacy.