Reincarnated into a fantasy world, a young man named Crow dreams of building a happy harem and becoming an unmatched hero. On a whim, he founds a guild, Akuma no Kaisen, also called Nightmare. To his dismay, the guild rapidly grows into the most powerful organization in the land, packed with incredibly strong and attractive members. Crow, however, remains the weakest of them all. His guild mates, all handsome men and beautiful women, adore him with a devotion that borders on worship, making any attempt to leave the guild impossible.

The story follows Crow as he manages a guild full of brilliant, powerful, and dangerously affectionate people while longing for a simpler, more peaceful life. The guild members fiercely protect and obsess over him, showering him with heavy love he often fails to recognize. Key members include Lulushira, a princess who proposes marriage after a forceful kiss; Galga and Horus, powerful beastmen with a shared past; and Pandy, a temporary leader from another guild whose domineering attitude causes conflict. The narrative spans several arcs: an investigation into a missing merchant that leads the group to the succubus country; the rescue of a runaway beastman princess named Yuyu, which draws them into a tournament called the Beastman King Succession War; and a guild leader exchange program that tests the bonds of the guild when Crow is sent to lead a different group. Later, the focus shifts to Crow's personal growth as dark emotions surface within him and he reluctantly faces the romantic attention of his members during a series of dates at a resort.