The "S" sibling relationship is kind of complicated. They have the potential to be a pretty awesome combination, but the factors that put strain on their relationship screw things up a lot. The fact he's very loyal to the Kairoushuu has a tendency to stamp out most of their potential for a normal brother-sister relationship. From Raimei's point of view, no good can come from the organization. They're willing to use people for their own gain, and just throw them away (like Yoite), and Raimei finds something seriously wrong with that. Figure in the fact that the Kairoushuu is responsible for the deaths of many of her Fuuma village comrades, and it all adds up to some pretty justifiable anger in her book. After fighting alongside them at Alya Academy, and meeting Gau, her opinions of individuals within Kairoushuu has changed, but not the group itself. She just doesn't get why anyone would want to be so loyal to someone like Hattori Toujuurou, and thus, Raikou is a dumbass for doing so. Part of her will always hope that he'll come to his senses, because she loves him, as any little sister would.

When united in a common goal, they do pretty well together. Being the calmer of the two, he can get her to keep a level head with a good smack to the face. She appreciates the way he balances her out, as much as she protests. She'll even grudgingly concede that he can give half-decent advice. She doesn't even mind the teasing, even though she gets irritated, because it seems to give things a sense of normalcy. And in the end, he's the only one who can really relate to her when it comes to the death of their clan. The fact that he carried the burden of truth alone bugs her a lot, but she understands that he did it because he loved her. Deep down, she loves him just as much-- if not, more-- which is why being enemies is so frustrating.