This is already really damn good for how early in development it is, kudos to the dev. I was going to say different camera angles would be nice, but lo and behold they're already in the itch.io version.
The only major things I can think of that would be really nice additions to have are
1: The girl's throat bulging out when she's got the dick deep enough,
2: More positions than just the girl on her knees and the guy standing, possibly even sex positions instead of just cock-sucking,
3: More voice options for people who aren't into really high-pitched anime girl voices,
4: Support for different head/penis shapes so that monster girl/furry characters can be included, be it the dev himself adding some options like that or just one to have as a base so that modders and such can make add-ons, and
5: The option to make the male character getting sucked another female with a strap-on or futanari instead, maybe even for it to be a guy doing the sucking for people who are into that.