Wrist watch shaped timing ignition devices for bombs are displayed by Japan's Meiji University at the museum of Japanese Imperial Army's Noborito laboratory in Kawasaki, suburban Tokyo on May 29, 2015. [Photo/CFP]

Those crimes have also been confirmed by former workers of the laboratory Tsujuo Shoji and Enji Ota. Showing some fake currency, they told Xinhua that "for the possible final battle, printing work continued until Aug. 15, 1945."

Shoji, 87, said: "Many of the bills were left after the war. Once they were found, we would be charged with war crimes, so I was ordered to destroy any evidence."

"I put some oil on them to burn all the bills, but the ashes could still be recognized, so we put the ashes in bag and threw them into a river," he recalled.

However, some of the survived counterfeit money and bomb balloons have been on display in the museum to remind people of the ugly truth of war.

"Those weapons and devices developed at Noborito Laboratory were unethical and illegal. We want more people, including our students, to know the realities of war and pass these down to the future generations," Yamada said.

He also expressed his opposition to right-wing politicians' attempt to whitewash the Japanese military's wartime atrocities and even deny Japan's aggression war against its neighbors during WWII.

"War and peace are not two extremes, but two sides of the same coin. To prevent the repeat of war, we need to learn the real history and reflect on our past wrongdoings. On this side, Japan needs to learn a lot from Germany."