According to the written confession of Masao Horiguchi in August 1954, he was born in Tokyo, Japan in 1901. He went to northeast China to join the War of Aggression against China in 1937 and served successively as unit commander of Dunhua Branch of the Japanese Xinjing Military Police and colonel and commander of Jinzhou Military Police.
August 1937: had a captured anti-Japanese patriot of the Anti-Japanese United Army "escorted to the highland on Paotaishanto the west of Dunhua County, and then ordered the subordinate sergeant of military police to cruelly behead that person with Japanese sword";
From the end of 1938 to August 1939: after interrogating with torture the 8 captured Chinese patriots, "sent 3 of them in special transfer (special punishment) to Unit 731 in Harbin";
June 1939: after a Chinese was tortured to death while being interrogated by the subordinate military police, "ordered them to bury the body in the mountains at night";
August 1939:the subordinates shot a Chinese to death during an arrest, ordered them "to throw the body into Mudanjiang River at night";
From August 1942 to August 1943: arrested a total of 80 anti-Japanese people, "with the permission and instruction of the commander of the military police, 20 of them were sent to Unit 731 in Harbin".