I've Been Killing Slimes for 300 Years and Maxed Out My Level

Just as peace is beginning to reign in Azusa's home, a young elf named Halkara shows up pleading for her help. Halkara says that an energy drink she made angered a terrifying high demon, Beelzebub, who is now out to kill her. Azusa would prefer to avoid anything that might ruin her slow life, but she can't just leave the poor girl to die, so she reluctantly agrees to shelter her...