I believe that there were many locals that were opposed to his release.. He killed 30 I think.
"The locals on Lubang came to call them the "Devils in the Mountains"
One day in 1959 Onoda heard what seemed like the voice of his own brother over the loudspeaker. The voice was pleading with him to give himself up. He crept to the clearing and took a look. He saw a man who appeared to look like his brother speaking into the microphone. Clever Americans. They have now really outdid themselves this time. They have gone to the trouble of finding someone to impersonate my own brother. Years later Onoda would learn that the man really was his brother. This is proof I suppose that it is impossible to convince someone of the obvious once they have their mind made up to the contrary.
Years went by. In 1965 Onoda and Kozuka stole a transistor radio from a local resident. They were able to listen to Japanese radio broadcasts. But again they either didn't understand what they were hearing, or they twisted it to fit their own preconceived notion that the war was still going on.
During the late 1960's and early 1970's Onoda and Kozuka got in the habit of setting the locals' rice fields ablaze as a way to signal their presence on Lubang to any Japanese forces that were close enough to see it. But in October 1972 the Filipino police set a trap and arrived at the scene before Onoda and Kozuka could make their getaway. In the ensuing gunfight Kozuka was shot dead. Now there was just one soldier left, Onoda himself.
http://www.tomandcathymarking.com/re..._surrender.htm