A photo from a vintage, April 1939, publication showing Nakajima E4N undergoing maintenance and although straightforward looking there are a number of puzzling details.
First, the photo was taken during a visit of the magazine reporters in IJN's Marine (Kaiheidan) training installations in Yokosuka. We were unable to locate any information about the Japanese Marines having any aviation unit or such.
Second, the kanji on the fuselage side is the first of the word "KYOiku" (education/training). This is an unknown marking, not corresponding to any known IJNAF unit.
Third, the type of the aircraft is also a puzzle. Are they E4N2 seaplanes with their floats changed to wheels or are they E4N2-C (later re-designated E4N3) of which very few were built? We tend towards the latter since the Yokosuka Kokutai had a few E4N3s and the seaplane E4N2 type was still in active duty.