Well, Ratri gets away with it because Kai acts like a total doormat sometimes. He's "happy" with whatver Ratri gives him, even when it is accompanied by humiliation (getting slapped in front of Narada) or borderline betrayal (volume 3?). It' both his noblest quality and his greatest flaw. Ratri does tend to relent, though and judging from his actions he realizes what a prize Kai is (something Kai doesn't even see in himself) and clings to him in whatever ways he can. In some ways they're truly a "stupid couple." They're both so adorably insecure about a relationship that has been completely codependent since the moment the first sleep together. ^_^