Kurumu Kurono is a succubus, and is initially jealous of Moka's popularity overshadowing her own, though she eventually considers Moka a friend. She tries to seduce Tsukune and the male student body, using her charming techniques (through her succubi abilities, including her busty physique), making them her slaves. This is so she can find her "mate of fate", in order to save her diminishing species, with the assumption that Moka is blocking her path. After Tsukune persuades the unsealed Moka to spare her, she becomes infatuated with him and makes a decision that he will be her "mate of fate", becoming friends with the pair.
While she does continue to tease and try to seduce Tsukune, it is clear that she possesses true and honest feelings for him- she's been shown to be willing to risk her life for him numerous times throughout the anime and manga. In the manga, Kurumu is 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. Despite this, an often running gag in both series is when she uses her 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. Also, no matter where they are, she somehow manages to interfere with any tender moment between Tsukune and Moka, often by appearing when least expected.
In an omake, Kurumu reveals she has a serious weakness for sweets, to the extent that she once ate poisoned cookies that she made and planned to give to Moka. The incident seems to have bought her some control over this trait, as the aforementioned love sweets are intact whenever they appear.
Described as a tough character, Kurumu sports a pair of bat wings, tail and razor-sharp nails in her true form, and has notable body strength (seen when carrying people during flight). The use of illusions and reality-bending techniques make up for her lack of combat abilities. Kurumu also carries a unique, innate sense of knowing when danger might occur. As of the second manga serialization, she is learning basic witchcraft.
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.
Kurumu's power is great even among succubi she is able to glide through mind barriers with ease... "It's talent of rather. It's the result of her wholehearted feelings."