"Welcome to Succubus High!" is a supernatural comedy manga set in a unique high school where succubi and incubi coexist with humans. The story centers around Haruto, a human boy who accidentally enrolls in Succubus High, a prestigious academy designed to train succubi and incubi in the art of seduction and energy harvesting. Unaware of the school's true nature at first, Haruto quickly discovers that he is the only human student, making him both a curiosity and a target for the supernatural student body.

The narrative explores Haruto's attempts to navigate this bizarre environment while maintaining his humanity. The succubi and incubi, who rely on absorbing life energy to survive, see Haruto as an ideal source of sustenance due to his pure and untapped energy. However, Haruto's resilience and determination earn him the respect of some students, including Lilith, a top-ranking succubus who becomes his primary protector and eventual love interest. Lilith is initially cold and calculating but gradually develops genuine feelings for Haruto, complicating her role as a succubus.

Throughout the series, Haruto faces various challenges, including rivalries with other students, the school's strict hierarchy, and the moral dilemmas of coexisting with beings who view humans as prey. The story balances humor with moments of tension, as Haruto's presence disrupts the status quo and forces both humans and succubi to reconsider their assumptions about each other. Supporting characters, such as the mischievous incubus Lucian and the shy succubus Mina, add depth to the narrative, each contributing to Haruto's growth and the evolving dynamics of the school.

The plot delves into themes of coexistence, identity, and the blurred lines between predator and prey, all while maintaining a lighthearted tone. As Haruto becomes more integrated into the school, he uncovers secrets about the institution's origins and its connection to the human world, leading to larger conflicts that test his relationships and resolve. The series combines supernatural elements with high school tropes, creating a unique blend of comedy, romance, and action.