Halkara, an elf girl, appears at Azusa’s home seeking help against the demon Beelzebub. She explains she created Nutri-Spirit, an energy drink, but it made Beelzebub ill so she fled to avoid punishment. Azusa agrees to take Halkara as her student and puts a barrier around her house. While gathering mushrooms Halkara carelessly eats one that has aphrodisiac effects and tries to seduce Azusa who punishes her. Azusa realises Beelzebub, the Lord of Flies, has been in the house disguised as a housefly the whole time. Azusa challenges her to a duel, during which Beelzebub flies into the barrier and passes out from shock...