Kurumu Kurono is a busty succubus attending Yokai Academy. Her outfit consists of a tight-fitting yellow sweater-vest with a red bowtie over a long-sleeved dress shirt and baggy socks (though she switches to a short-sleeved version of her outfit with a red ribbon tied in a bow from the Witch's Knoll arc onwards). She was initially a rival to Moka, being jealous of her popularity surpassing her own, and attempted to seduce Tsukune and the male student body to find her "Mate of Fate", as her kind is near the brink of extinction. 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 "Mate of Fate".
A running gag in both series is when she uses her characteristically large breasts (said to be a G-cup according to her in an omake) 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. Ironically, Kurumu has a serious weakness for sweets as revealed in an omake, where 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 fiancée. Mizore's nickname for Kurumu is "Bazooka Girl", and Kokoa refers to her as "Twin Peaks".
Throughout the series, it is clear that she possesses true and honest feelings for Tsukune, as she has been shown to be willing to risk her life for him numerous times. As mentioned by Kokoa in the second serialization, Kurumu is "pure of heart" compared to other succubi as she doesn't use her techniques to try to make Tsukune fall in love with her. Kurumu has also shown to be a kind and soft-hearted girl who loves her rivals for Tsukune's love like sisters, tenderly comforting and supporting them in their moments of sadness as well as defending them when they are in danger. This kind-hearted character-trait is downplayed in the anime in favor of a more typical "flirt" character, although the kind-heartedness is still present, and in reality, she is actually an innocent character. Her catchphrases throughout the anime series are "Yahoo-hoo!" and "Bow-wow!", and always somehow manages to interfere with any tender moment between Tsukune and Moka, often by appearing when least expected.
As a succubus, Kurumu possesses the power of "Charm" (called "Allure" in her introductory chapter), which she can use to hypnotize males. According to legend, if a succubus kisses a male while he is still allured, he will become her permanent slave. In her true form, she sports a pair of bat wings, a tail, razor-sharp nails, and pointed ears, 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 pin-up 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 along with Mizore, and 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. As a result, she and Mizore also have a joint attack called the "Black and White" duet. Some further abilities Kurumu later employed in the second serialization is the ability to enter the dreams of other people via her tail (though she claims she never used this ability), as with the case with Inner Moka, but prolonged use of the ability will wear her body out. It is later revealed in Chapter 40 that succubi gain their power from their loved ones, and a succubus who is not loved will eventually die (which explains why Kurumu's body feels weakened due to thinking that Tsukune will choose Moka over her). So in an attempt to save her life as well as Tsukune's (while out of control in his demonic form), she kisses him while confessing her love to him in the following chapter