Hi, Hermann...
'G9' is the identifying code of the parent Geschwader, in this case Nachtjagdgeschwader 1. 'G' is the indivifual aircraft I/D letter, and 'V' would identify the Staffel in which the aircraft was operational. 'V' would normally have indicated the 11.Staffel of IV.Gruppe.
There is a book -
Luftwaffe Emblems 1939-45 by Barry Ketley & Mark Rolfe (Hikoki Publications) - which has a similarly coloured machine on the outside of the back cover, again with an overall black colour scheme, but on this occasion, coded 'G9+JN'. This would appear to state that the aircraft was from NJG1 (G9), aircraft 'J', within 4.Staffel, denoted by 'N' as the last character, therefore within II.Gruppe. The caption inside referring to this plate, however, claims it is a III.Gruppe machine, in which case, strictly speaking, the last letter should have been 'S', indicating 8.Staffel within III.Gruppe. Unfortunately, I have no information as to whether or not the kit, or specific markings, relates to an ace or not.
Great care should be exercised, however, with the codings of Luftwaffe aircraft in general, because oftentimes, machines were 'loaned out' or transferred to other sections of the same squadron, or indeed, to other squadrons altogether, as necessity dictated. Their codes were not always changed at their new unit before being deployed into action.
Lastly, many of the nightfighter units did use Bf110s and other twin-engined aircraft, but single-engined machines were not infrequent within their ranks, especially early on in the war. The Luftwaffe High Command had not really considered the threat of night bomber attacks to be something worthy of consideration in the early stages of the conflict, so when they did wake up to the reality of the situation, they tended to employ anything suitable that they had to hand. The sub-verson of the kit you mention is actually an early version, a Bf109E. Other sub-types of the Bf109, and Focke-Wulf Fw190s as well, were also used during the course of the war in the single-seat night-fighter category. Hope this is of help to you...
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Incidentally, is the kit you refer to not 1/32nd scale, as per the website of the toy company...?
Regards...