"Secret Battle of Guadalcanal"
by D. Jenkins via Sydney Morning Herald May 7, 1974 via “War by Stealth” by Alan Powell about the A.I.B.

"The Japanese also had a coastwatcher on Guadalcanal – Lieutenant Commander Kenji Mitsui, landed by destroyer near Lunga on 4th October [1942].  From a ridge above Henderson Field he watched the progress of the battle, reporting American aircraft losses to Rabaul.  Through the ability of the US Navy’s ULTRA (codebreaking) organization to read Japanese naval codes, the Americans soon knew that Mitsui was there, but the terrain and the jungle that sheltered the Australian coastwatchers sheltered him too.  He lived to be taken off Guadalcanal by submarine on 25 January 1943.  The Allies encountered signs of other Japanese coastwatchers in New Guinea and New Britain yet never, it seems, was any attempt made to organize a systematic coastwatching service to match the Australian effort."