Guy, guys. You are being incredibly shallow yourself if you think this is all hinging on whether or not Akari's lover was a virgin.
Throughout the 8 pages, Akari treats their relationship as if it's something special, and her lover continually treats it as if it's not (example on 2nd page: "That means our body weight has increased, doesn't it?" = "We're in love" as opposed to "Yeah, maybe." = "Maybe, maybe not."). The problem was that her lover treated their relationship as just something to have fun with, while Akari thought it was serious for both of them.
Akari being a virgin just meant this was all new and exciting to her, while to her lover, it wasn't. Again, just showing the difference in perspective of the two involved in the relationship, each thinking it meant something different.
Akari didn't fall out of love with her lover just because she wasn't a virgin. That was just one other element of many that lead Akari to realize her lover's interpretation of Akari wasn't nearly anything like how Akari was feeling for her lover. And this realization itself led to her falling out of love.
If anything, my take on the story was that it was about an immature, inexperienced girl growing up a bit, and realizing, with a pang of sadness, that not everything is what you may think it is. Not that your lover has to be a virgin, hahaha.
You need to at least dive below the surface before you can begin to tell how shallow something is.
I think you hit it right on the mark and this is my interpretation of the story too! Nice below-the-surface analysis! ^_^
