I don't know what's being said exactly, but I think Ryouma just remarked that Kamui's chest has gotten bigger (or at least Hinoka THINKS Ryouma was talking about Kamui's chest). EDIT: Oh hey, I was right.
Updated
You've gotten big.I'm talking about her height!His sister forgave him for that...!You were still so small when we separated....Female Kamui meeting her Byakuya siblings again.What did?