Look at it. It's white and viscous. When the females cum in the dev's series it's usually a spray of droplets while they shudder.
This was him hilting with force and the cream surrounding his cock like creampies tend to do in hentai.
Doesn't have to mean she was cumming at the moment. Pussy juice can be clear yeah, but it can also be cloudy or white. Or if you been fucking a chick for a bit, the friction of ur dick and her juices can turn it white as it congeals n shit. If you ever seen or heard of 'cream' during sex, that's usually what that is. What blud said could very well be correct.
At the same time tho, you don't usually see that shit depicted in games. Wetness be like water most of the time, and you never be seeing cream. I don't rem the exact depiction of the liquid ur talking about, so you also could very well be right. I could visualize that being a plot point, or maybe a immediate point of contention between the two off rip in the update.
I'm imagining that in part 2, Asuna letting bro fuck without a condom will be a further point of corruption, so who knows where that could go or how shit is used.