Ririko Kagome is a bespectacled math teacher at Yokai Academy and a lamia appearing in chapter 12 of the first serialization. Seemingly innocent and deeply concerned for her students' grades, she offers private lessons to anyone willing, though at a price (according to Kurumu, Ririko tends to go overboard with her tutoring, and envies her for her large breasts). As such, she uses her abilities to drain her students' emotions in exchange for knowledge, which is done through a flower-like appendage on her tail. She also seems to have a fetish for S&M outfits, claiming that it makes her male students "work harder".However, this might be only what she thinks in her warped mind.

In both the manga and anime series, Ririko tries to enslave Tsukune when he is forced to have tutoring by her in order to correct his failing grades in math, and believes that Moka is in the way of his studies (she caught Moka trying to suck Tsukune's blood, but misinterpreted it). But when Moka attempts to rescue him, Tsukune snaps out of Ririko's control long enough to remove Moka's rosario, leading to her defeat by Moka's vampire form (she was given a two-week suspension according to Tsukune, meaning she will be allowed to return to work, unlike Ishigami).

She reappears later in chapter 19, apparently not holding a grudge, to warn Tsukune and Moka about Okuto Kotsubo. While she no longer bears a grudge against Moka in the manga, her grudge against her remains in the anime, shown when she attempted to take Moka hostage only to be stopped by Nekonome in a catwoman costume. Also, her anime incarnation is slightly more perverse than her manga counterpart. It is important to note that unlike other antagonists, she is not inherently evil, but rather very passionate about the education of the academy's students as well as the status between teachers and students.