The director Kiyoshi Kurosawa is best known for horror movies depicting the dark undercurrents of life in modern Japan and the vengeful ghosts that haunt it.

But the evil spirits lurking in the background of his latest film are a real-life horror from the country’s past — the Imperial Army’s testing of biological and chemical weapons on human subjects in Manchuria before and during World War II.

The movie, “Wife of a Spy,” garnered Mr. Kurosawa the award for best director at the Venice Film Festival last month. When the film is released in Japan this month, it is likely to cause a stir in the country, where wartime atrocities remain the subject of intense controversy and are seldom seen on the big screen.

Winning a top prize at an international film festival is a major victory for Japan, which has invested heavily in promoting its culture industry through its Cool Japan program. But Mr. Kurosawa’s honor may prove awkward; the nation portrayed in “Wife of a Spy” is one that Japan’s vocal right wing, including members of the government’s upper echelons, would rather be forgotten, and have worked to erase.

Japanese missions abroad routinely criticize depictions of the Imperial Army’s wartime brothel system, where women were often forced into sexual slavery. In Tokyo, black vans often prowl the streets spouting propaganda that rewrites the country’s role in the war. And publishers churn out books disputing the most basic facts about atrocities.

No matter their ideological lens, Japan’s war movies have largely ignored the victims of Japan’s imperialism. The right fetishizes the country’s martial spirit and quiet endurance, while the left tends to deplore the suffering of soldiers in the field and civilians at home.

In a recent interview, Mr. Kurosawa, 65 — no relation to the famed director Akira Kurosawa — said he found it hard to understand why Japan’s war crimes remained almost taboo among the country’s filmmakers 75 years after the conflict’s end.