@KeiosKod
I get what you're driving at, and I do think that banter should have almost no limits. But some things you don't really bant about, and this is it.
When banter over a subject that hits emotionally so close to a person, that it gets indiscernible from friendly banter and psychological manipulation means it should at least be done in a limited manner, if not a barred subject.
Ryuugasaki is very well aware of Ushiwaka's feelings, and so is the man in question himself aware as well. To then make light of his emotional state, and toy around with him is indicative of either 1) emotional immaturity, 2) lack of empathy for his well-being, 3) A little bit of both.
This is what I mean when I refer to Ryuugasaki as a narcissist. Not the cutesy, anime "Oh look, he admires himself too much in the mirror, he's so quirky" narcissist, but in the full-blown "he manipulates those around him to feed his own ego" narcissist.
Of course, them being so young means I'm more leaning to "This guy is a social idiot" rather than "He really just doesn't give a damn about his childhood friend as long as he gets something out of him."
As long as they're both behaving honestly, it's all good and well, but I got a gut feeling from experience that tells me Ryuugasaki isn't exactly doing that.
But at the end of the day, they're both fictional characters, made as reflections of the author's thoughts, so real life experience may not necessarily apply here.
Toying with someone in such a vulnerable emotional state, in terms of romance, just comes across as more mean-spirited than friendly banter.
On the flipside, Ushiwaka is as much of an idiot for lashing out at his surroundings instead of getting himself under control and making calm, well thought-out decisions afterwards.
But again, you don't expect this level of maturity from a 17-18 year old to begin with, I suppose.