This is a modified airsoft gun: the WE G26C Advance (Tan). It is in fact a knock-off of a Tokyo Marui airsoft pistol, the Glock 26 Advance, which was featured in (and perhaps created for) the Ghost in The Shell: Stand Alone Complex TV series.
There are physical differences between the two pistols: The color of the body (which appears to be the original, unpainted tan plastic on the prop), and the full auto / semi-auto selector switch on the slide, which is not present on the Tokyo Marui. It appears that the barrel and guide rod have been extended, white marking have been applied to conceal the engraving on the slide, and there is an unknown accessory screwed to the slide (?) as well. It’s possible the prop uses a black grip extension on the base of the magazine (as opposed to the stock tan), but the screencaps are inconclusive.