Reirin is totally mary sue character. I'm so dissapointed with keigetsu's character development. The author has many chance to make her matured and changed for real but no they decide to give Reirin to take the spotlight from Keigetsu everytime she can prove her worth. Reason : "because I want to protect keigetsu" Don't give me that bullshit, at this point Reirin is just a control freak and manipulative perfect maiden that befriended a "lowly villainess" that are worse than her. Friend are supposed to walk along with you not do things you can't in your stead everytime.
They remind me so much of Eiden and Yakumo from Nukani