Familiar Spirit of the Demon Lord (魔王の使い魔)

Today is the 2400th birthday of the prince of the demon’s realm (you).
You make a lot of effort in a demon summoning ritual in order to have
your own familiar spirit, but a human girl is summoned instead of a demon…!?
Even though you are the expected next demon lord, people may underestimate your magic ability… You have to prove your ability by making the human girl into a demon!