Hiro Shizuki he's was always bullied for being weak he wants to get stronger but nothing working for him one night he had a dream of a girl who called herself Beelzebub and told him to find her upon meeting Beelzebub and the other mortal sins Hiro learned Beelzebub is his grandmother and her blood flows through his veins it explains his eating habits and his quick recovery because he's half demon after training with his family he earned the title of Demon Lord from Lucifer herself this is when the seven heavenly virtues appeared the angels sensed a familiar power in the boy to Beelzebub and realized his is a decentant of Beelzebub so her rival Raphael decided to watch over Hiro sense a good heart in him eventually Raphael became his girlfriend they return to Union and they're surprised to see the new Hiro.