Kurumu Kurono is a succubus who was introduced in the second chapter of the manga and episode 2 of the first anime adaptation (she was seen in episode 1 but was never introduced). She was initally a rival to Moka, being jealous of why she is more popular than her. After she was badly beaten during a fight with Inner Moka, Tsukune persuades Inner Moka to spare her, and as a result, Kurumu not only became friends with the pair, but also becomes infatuated with Tsukune and makes a decision that he will be her "Destined One". A running gag in both series is when she uses her large breasts to seduce Tsukune, which, more often than not, makes his nose bleed and causes him to suffocate. She also attempts to use baked sweets laced with love potions to secure his affections, though they never seem to reach him. In an omake, Kurumu reveals she has a serious weakness for sweets to the extent that she once ate poisoned cookies she made and planned to give to Moka. Kurumu's mother is Ageha Kurono, who appears during the start of the school festival under the belief that Tsukune is her daughter's fiancé. She has a habit of saying "Yahoo-hoo!" and "Bow-wow!" when excited, and always somehow manages to interfere with any tender moment between Tsukune and Moka, often by appearing when least expected.
While she does continue to tease and try to seduce Tsukune, it is clear that she possesses true and honest feelings for him, as she has been shown to be willing to risk her life for him numerous times throughout the anime and manga. Kurumu is also shown to be a kind and soft-hearted girl who loves her rivals for Tsukune like sisters, tenderly comforting and supporting them in their moments of sadness as well as defending them when they are in danger. This was toned down in the anime, where she is the more typical "flirt" character, though the kind-heartedness is still present and in reality, she is actually an innocent character.
Being a succubus, Kurumu possesses powers of "Allure" (called "Charm" in the anime), which she can use to hypnotize males. According to legend, if a succubus kisses a male, he will become her permanent slave. Kurumu sports a pair of bat wings, tail, and razor-sharp nails in her true form, and has notable feats of superhuman strength (seen when carrying people during flight and slicing trees in half). Later on, Kurumu displays further powers employing the use of strong illusions, once doing so to wrap vines around a slug yōkai who was blackmailing to take ecchi pictures of her. Despite being sealed, Inner Moka was stunned that Kurumu displayed such power, as the power of illusions is usually displayed by higher-ranked succubi. In the second manga serialization, she is learning basic witchcraft to help with the strength of her illusions and along with Mizore and she was trained by Ginei during the summer break in hand-to-hand combat in an effort for the two to become strong enough to overcome Inner Moka in a fight. She is roughly the second strongest female in the Newspaper Club, although many consider her and Mizore to be about par level overall. She and Mizore have a joint attack called the "Black and White" duet.