Kurumu Kurono is a Succubus and the second most beautiful girl at Yōkai Academy. Initially antagonistic towards Tsukune and Moka, Kurumu grows to become one of their best friends. And despite her numerous sexual advances towards Tsukune, Kurumu is actually a very innocent character and genuinely yearns for Tsukune's love.
It is hinted that should Tsukune not pledge his love for Kurumu, she will die, as the source of love (especially more so from her Destined One) is her source of life and power.