Men Behind the Sun

Two hundred Japanese boys are conscripted into the Youth Corps and sent to a Kwantung Army facility linked to Unit 731. They are quickly exposed to brutal experiments and feel a deep revulsion at what they witness. The film opens with the line 'Friendship is friendship; history is history,' framing their entry into this dark world.

Shortly after arrival, the boys are introduced to the experiments and the chilling methods used. The staff reveal that the research aims to find a highly contagious plague to weaponize against Chinese civilians. The boys feel revulsion and begin to understand the scale of the brutality they are among.

They befriend a local mute Chinese boy whom they play games with. The friendship provides a counterpoint to the cruelty around them and offers a glimmer of humanity amid the terror.

An order is given to bring the Chinese boy to the facility, and the youths naively comply, believing no real harm will befall him. They accompany him inside, unaware of the fate awaiting him.

Inside, the senior medical staff vivisect the boy while the youths watch in horror. Realizing the atrocity, they stage a minor uprising and beat their commanding officer in protest.

Dr. Ishii develops a prototype ceramic bomb that preserves fleas inside, aiming to create a more effective delivery system. He moves the project forward, showing little regard for the human cost of the experiments.

To test the device, several Chinese prisoners are tied to crosses for exposure. The test is botched as Japanese aerial forces retreat; Chinese prisoners break free while Japanese troops hunt them down, and many are killed, including some Japanese soldiers.

Unit 731 overhears the atomic bombings of Hiroshima and Nagasaki and Russia's declaration of war. Ishii orders his subordinates and their families to commit suicide, but is persuaded to evacuate them and only allow suicide if captured.

That night, Unit 731 destroys evidence of their research and blows up the facilities. Surviving test subjects are gassed to death as the project is scrubbed from history.

The Japanese troops and their families wait at a train station to return home to Japan. A lone survivor, disguised as a Japanese soldier, attacks one of them but is impaled by a Japanese flag. The Youth Corps clutch the blood-stained flag in horror as they depart.

In the closing moments, Ishii cooperates with the Americans, providing them his research and agreeing to work for them. Years later he is moved to the Korean War era, where biological weapons appear on the battlefield.

The youths involved with Unit 731 bear the weight of their past for decades, leading hard lives after the war. Their educational backgrounds and associations are stigmatized, shaping their futures.