Heresy was born and raised in a remote farming village, but he has always dreamed of becoming a summoner. Thanks to a special friend he made when he was little, he gets to turn that dream into a reality. That friend is Happy, his summoned beast, who is a kind and innocent girl, even if her appearance as a harpy is slightly monstrous and unusual.

Because of Happy, Heresy is deemed worthy to enter the Meilleur Royal Summoning Academy, where he hopes to begin an exciting school life making friends and sharing precious moments. However, Heresy quickly finds himself an outcast in the summoning academy. Though he simply tries to live an ordinary life, his unique partner causes misunderstandings at every turn. He unintentionally terrifies an arrogant rich girl with Happy's frightening appearance and even summons a second bizarre beautiful girl, causing chaos throughout the school.

The situation escalates when Heresy is falsely accused of being the mastermind behind a conspiracy completely unrelated to him. To save the academy from a crisis he was inadvertently swept into, this unlikely boy and his cute yet terrifying summoned beast must stop running from misunderstandings and reveal their true abilities.