During World War II, under the authority of Lieutenant General Shiro Ishii, Unit 731 conducted multiple classified experiments in occupied Harbin. During the Second World War, Unit 731 was created by the Japanese government to implement a public health program for Japanese soldiers. The Unit's objective was to learn how soldiers can withstand hunger, thirst, and diseases. Early experiments were conducted with the permission of volunteers who signed up for the program. However, the unit secretly changed its methods. The leader of Unit 731, General Shiro Ishii, assembled a group of scientists intending to develop new weapons for the Japanese military during the war. The Japanese government managed to destroy most of the records after the war, and little was known about this incident. Yet, some documents were leaked and exposed later. Under the command of Shiro Ishii, the unit was conducting detrimental experiments on humans. Normally, volunteers were reluctant to participate in such experiments. For that reason, Unit 731 decided to use war prisoners as their test subjects, and these prisoners were mostly Chinese and Russians. Unit 731 was divided into two departments. The first one, the Department of Chemistry and Biology, attempted to create new diseases. By using their test subjects, referred to as "Maturas", scientists infected prisoners with multiple germs to observe disease progression and test potential weapons. The leaked records revealed that certain germs had been tested, through vivisection, such as Yersinia Pestis, Bacillus Anthracis, and Syphilis. Although these torturous methods were unethical, illegal, and immoral, Unit 731 workers considered it a necessity to win the war. The Unit's victims were also split into two groups, males and females. In order to study the transmission of diseases, Male subjects were ordered to indulge in forced sexual intercourse with female prisoners. Scientists unmercifully conducted experiments on impregnated females to study the effect of these germs on mothers and their fetuses. Most of these experiments ended in failure, resulting in the closure of the Department of Chemistry and Biology and the destruction of evidence. Meanwhile, the Department of Quantum Physics continued its experiments even after the end of the War. A few leaked documents revealed the type of experiments conducted by the second division. Journalist Yamamato Tochiba had the opportunity to interview two former scientists who were involved in the program: The Hayasaki couple, Haruto and Asuka. Both were physics professors at the University of Tokyo before being drafted into the war. Hayasaki Haruto, at the age of 24, was initially compelled to serve as a soldier and participated in early-war battles and expansions, while his wife, Hayasaki Asuka, aged 23, was assigned directly to Harbin as a researcher in Unit 731's Second Division. Though separated by a long distance, the Hayasaki couple clung to each other through letters. They both managed to communicate by sending threads of news, hope, and love across the landscape. Those letters were later seized and burned after their assassination, erasing traces of any communicated information, and leaving behind their only child. As the war dragged on, the husband abandoned his post as a soldier and made his way to Harbin to join his wife and support her during the darkest chapters of their lives. After the end of the war, the Hayasaki couple managed to leave Harbin and continue their lives as teachers in an elementary school. On February 12, 1980, the Hayasakis were found assassinated in their apartment under mysterious circumstances. Despite continuous investigations, the police couldn't find any leads, and the case was officially closed in 1985. In the years before their assassination, journalist Yamamoto Tochiba managed to interview the Hayasaki family a couple of times to cover the stories at Harbin. After their death, Yamamoto published a heartfelt apology in Shūkan Gendai, expressing deep remorse for any role he may have played in exposing them to danger, and then he announced that he had adopted their only child. Leaked records suggested that the Second Division had been developing a time leap machine, though such rumors weren't officially confirmed. Initially, the Quantum Physics Department focused on creating time-leaping machines in an attempt to send soldiers into the past. According to some documents, their ultimate purpose was to secure a victory in the war and prevent the atomic bombing of Hiroshima and Nagasaki. Rumors also hinted that the Second Division used humans as test subjects in their experiments, though the nature of these procedures had remained hidden. Another rumor claimed that the failed test subjects referred to as "Nekros" were buried in an unmarked area in Harbin, where Unit 731 workers buried all the bodies, placed layers of rubble and broken bricks over the bodies, and sealed their graves with cement. In several interviews, Yamamoto pressed the Hayasakis for details about the human experiments carried out in Harbin and the true purpose of Unit 731. However, Haruto and Asuka refused to disclose any classified information for their own safety. Eventually, Haruto entrusted Yamamoto with his personal diary, in which he had secretly recorded the everyday life at Unit 731.
