I was studying the well-known Akeno Hayate film, pursuant to something else entirely (but not wearing my anorak), when I noticed something interesting for the first time. There is a "coating" along the whole length of the fuselage, broken only by the natural metal reflection just below the cockpit and at the wing root. At first I thought that this was just non-reflection of the metal surface - but it isn't. It appears to sit over the sparse green mottle, which makes me think it is some form of residue from the engine (oil?) or staining from the exhaust, but I'm not sure. If it is the latter then it is not the type of staining usually associated with exhaust effluence as it appears to have spread a fine and constant film along the whole length of the fuselage. Perhaps the result of that "fan" of thrust exhaust pipes? If it is oil maybe that is what is so engaging the two groundcrew's attention?
Is it overspray from the mottle? Don't think so - too smooth and regular. A coating over the natural metal? Maybe. But as mentioned it appears to be over the green mottle not the other way around. This "coating" runs to the length of the tail and also appears to be the cause of the "greying" of the Hinomaru border but more curiously seems to be over the wings too, which show little or no reflection from the natural metal at all. The latter may be just be the result of a denser mottle applied to the wing upper surfaces as discussed before. Whatever it is it's probably worth a passing thought if and when reproducing a Hayate scheme like this.
Image credits: Akeno Ki-84 film stills author collection.