男鹿辰己(小西克幸 配音)就读于石矢魔高校一年级,是一个眼神凶恶个性粗暴的不良少年。这一天,刚刚在河边结束了一场斗殴的男鹿发现河面上居然飘来了一个长相十分可疑的大叔,更让男鹿震惊的是,大叔的体内居然产出了一个小小的婴儿!大叔告诉男鹿自己名叫阿兰德隆(高木涉 配音),婴儿名叫小贝鲁(泽城美雪 配音),他们来自魔界,而此行的目的就是毁灭全人类! 莫名其妙之中,男鹿与小贝鲁签订了契约成为了小贝鲁的奶爸,这一颠覆性的改变让男鹿觉得十分头痛。随后,身材和个性都很火爆的恶魔女仆希露迪(伊藤静 配音)来到了男鹿身边。一面要对抗校园中的黑帮团体,一边又要照顾个性别扭的小贝鲁,男鹿惊险又温馨的奶爸生活即将拉开序幕。The story follows the strongest juvenile delinquent, Oga Tatsumi, he is a first year in Ishiyama High, the school for delinquents. The story starts as he is telling the story of how he found the baby to his best (and only) friend Furuichi Takayuki. One day while fishing by the river (actually, taking revenge on people trying to kill him in his sleep), he sees a man floating down it, he pulls him to shore and the man splits in half revealing a baby boy. This boy is the son of the demon king and he has been chosen as the one to raise it with the baby's maid Hilda. The story follows his life with the child and at the delinquent school. The early chapters of the manga follow Oga as he attempts to 'pass on' Baby Beel to other students at Ishiyama, (The theory is that if Oga can find someone more evil and stronger than him, Baby Beel will attached to that person instead of Oga). After subsequently fighting and defeating all members of the Touhoushinki and in the process, destroying Ishiyama High itself, Oga and company are transferred to Saint Ishiyama Academy, which appears to be a direct opposite of the delinquent school.