Sai Akuto aims to become part of his country's highest order of magicians and contribute to society as one of its clergy. On the day he is admitted into the Constan Magical Academy, his aptitude test predicts the following though: "Future Occupation... Devil King". Thus begins his difficult school life in which he is resented by the combative female class head, Hattori Junko, desired by a girl with mysterious powers, Soga Keena, and guarded by a beautiful female android, Korone.
Chiyo Sakura confesses her feelings to her schoolmate Nozaki. Due to a misunderstanding, Nozaki thinks Chiyo is just a fan. She then discovers Nozaki's other identity; a shōjo manga artist. As she gets closer to Nozaki, she befriends Nozaki's quirky acquaintances who assist him and serve as inspirations for his manga.
A girl named Mitsuki Kanzaki lives with her step-brother Yuya after her mother remarries. One day, Mitsuki is possessed by the self-proclaimed spirit of a young girl, Hiyori Kotobuki. Hiyori (in Mitsuki's body) must fall in love with Yuya to move toward the "Gates of Heaven."
In another dimension the Devil King Sadao is only one step away from conquering the world when he is beaten by Hero Emilia and forced to drift to the other world: modern-day Tokyo. As "conquering the world" are the only skills the Devil King possesses - and are obviously unnecessary in his new situation - he must work as a freeter to pay for his living expenses.
Despite Ryuji Takasu's gentle personality, his eyes make him look like an intimidating delinquent. Class rearrangements on his second high school year put him together with his best friend, Yusaku Kitamura, and his hidden crush, Minori Kushieda. Along with these two comes Kushieda's best friend, Taiga Aisaka. Her delicate appearance contrasts with her brutal personality. Secretly in love with Kitamura, Taiga agrees to help Ryuji with his love interest as long as he helps her get closer to hers.