Ah, pure fluff like this soothes my soul. Also, is that credits page true? Because if so, that's kinda awesome.
A small bit of searching suggests they've gone on a couple dates. I'm unsure if these were serious dates or more along the lines of hanging out with a friend and refering to that as a date. It'd sure be neat if they were dating though. Also surprising, if they were intending to do so openly.
On topic: I'm not usually a fan of Ruby, I think something about her design rubs me the wrong way, but I enjoyed this a lot. I can't quite place why, but something about the art makes her seem more... mature than usual.
Tooth rotting fluff aside, their relationship and dialogue felt very natural. That might explain the more mature feeling I got, actually.