The Unkai Maru was originally a British steam ship with the name of S/S Venus built in 1903. She was bought by the Japanese in 1911 by Nakamura-Gumi Ltd. Being requisitioned by the Japanese Navy on January 5th 1944 she arrived in Truk on the 30th of January.
She was sitting there nearly empty waiting for cargo. The most likely explanation is that she got set on fire by some bullets even though the reports from the Americans say she got a torpedo hit and or several bomb hits. However, there is no visible damage on the hull. Burning through the day, the night and the next day she was still afloat when the planes left.
