Kei Niitoki has the tendency to stick her nose into other people's business; once she sees a problem, she wants to fix it. This personality tick lead her to becoming the president of Shinyou Academy's moral's committee. Most claim that it's a good fit for her, and some even call her a big sister despite her short stature. Though, Kei finds her tendency to get involved troubling. It's more of a compulsion rather than any kind of lofty ideal.

She also has a crush on Keiji Takeda, Touka Miyashita's boyfriend. This, compounded with the fact that Kei knows who Touka "really is," leads to Kei having a strained relationship with Touka.