It's kinda funny but I guess I could suggest reading some romance VNs and bailing before it gets bad. Like, read the common route of Grisaia no Kajitsu and just stop before the route decisions.
Other than that, I give up. The Lily route of Katawa Shoujo is the closest thing I have.
There are plenty of anime and manga that are pure fluff without any conflict, so I get where you're coming from with your request, but because VNs are released as a finished story from start to end they're guaranteed to have something for plot progression.
Wait, actually... if anyone here plays them, maybe one of those hentai VNs that are nonstop sex and dating? I wouldn't be surprised if some of them have no conflict or drama whatsoever. No?
What nukige? I suppose you might be able to find some, but even though their plot is minimal...it's not like they don't have one so there's still some wading through darker stuff to get something "vanilla" if that's what you desire.
*of course I'm at the top of the page *sigh*