Anime Like High School DxD
Rosario + Vampire
This anime like High School DxD hits the monstrous girl harem trope squarely on the head. The anime features many stereotypical monsters that most audiences are probably familiar with (like vampires and witches) as well as monsters that are mostly associated with Japanese mythology (like snow fairies).
The story follows Tsukune Aono, an average high school boy who accidentally ends up enrolling in a school for monsters. On his first day, he overhears that humans are forbidden on campus and killed for trespassing. Although he initially plans on leaving as soon as he gets through his first day, he meets and befriends a kind vampire named Moka Akashiya. She discovers he is a human and he discovers that she wears a rosary around her neck that keeps her true personality (a ruthless and arrogant warrior) tucked away so she can be a kind and bubbly person. They agree to keep each other’s secrets, and Tsukune decides to stay at the school.
Most of the anime’s plot revolves around efforts to keep Tsukune’s human nature a secret from the rest of the school, or Tsukune and Moka’s attempts to help other students that get into trouble. Most of these other students are girls, and they all take a liking to Tsukune. How Tsukune treats his friends is very much how Issei treats his ever-growing demon harem. The difference in these two shows is that Tsukune doesn’t want a harem. In fact, he mostly just wants a normal life and is completely oblivious to the fact that all the girls around him are fighting for his affections.