In this photo from a vintage publication, two Mitsubishi G3M2 Model 21 “Nell” bombers can be seen operating from mainland China before the beginning of the Pacific War. Note the hastily applied camouflage over NMF surfaces and the properly painted black engine cowling.
The three-bar rank insignia on the sleeve of the pilot on the left indicates that he is probably a commander (“chusa”); his colleague is probably a captain ("taisa", four bars). Some pilots chose not to wear these insignia, which were always on the left sleeve and became smaller in 1944.
The one-piece uniform is a winter version of the Type 9 (1934) featuring a rabbit fur-lined collar (the official colour was black) and zippers on the sleeves; the summer version lacked the fur and had buttons on the sleeves.
Last but not least, note that each pilot is carrying a Nambu pistol in a holster, which in the case of the pilot on the left carries his name in white.