Summon Night: EXTRA

The protagonist is Maruo, a 10 years old Summoner with barely any experience who feels overshadowed by his father's skills. One day, he accidentally brought upon a disaster by summoning the wrong person he was meant to choose, an evil demon king. Since then, everyone blames him for this and people want him executed. Afterwards, Maruo notices a girl getting attacked by monsters from the demon king. He tries to help her, but her rebellious nature prevents him from doing anything else. She then introduces herself as Kelly, the tomboyish princess of Acro Land. Later, Maruo would meet more companions, including a fighter and a cute ghost girl with a dark past.