You're probably right, considering how often people are shown confessing "love" to someone they have never even had a real conversation with. Most of these confessions are obviously based on the most superficial knowledge and acquaintance of the other person, and often seem to no more than liking that person's appearance and general reputation. You can't even say at that point that there was chemistry, as often the confession is the first real interaction the two have. So it probably wasn't a BF/GF relationship the way we would understand it.
Uh, except that he DID 'sleep' with Rin. As soon as he accepted her confession they WERE BF/GF no matter how anyone 'understands' it. T.
What I saw was Sousuke's hand reaching out to pull Rin off the edge of a cliff. Rin was already walking away, feeling rejected and being resigned to it. Sousuke caught him back. It was that or let the love of his life fall away from him forever. Fuck the girl.
Since the comment appears to be to me, I'll answer. First, he didn't actually sleep with Rin until after that phone call breaking up, though they did relieve themselves together. Second, not all relationships are equal and should be treated the same way. If she confessed with them being practically strangers, and not really having talked, not only was her feelings pretty shallow to begin with, but she had no reason to expect him to feel much for her. I know at one point Sousuke replies at the end at the phone call that he loves her too, but I have an elderly neighbor who's constantly telling me the same thing rather forcing me to respond in kind, even though that isn't quite the way I feel (I just like and enjoy their company). I very much doubt that Sousuke and his GF had more than a few awkward dates and phone calls, or that they were at all close.
That is the problem of the whole confession thing, it often seems to be people confessing to people they don't really know, which means whatever they think they feel is built on a fantasy of the other person. Being on the receiving end of that is probably kind of weird. It is likely not most comfortable thing to have all this supposed "love and affection" from someone you know doesn't really know or understand you, and who now wants you to feel the same way about them.
Everyone's talking about how that was pretty savage to break up with his GF over the phone but consider this:
They weren't really that close (he said she confessed to him and he was kinda just going along with it to see what happened), and it would have been twice as shitty of him to sleep with Rin without breaking up with her at all. He can always explain things to her face to face later, but I think he did the right thing. o3ob