After Clearing the Level, the Demon King Became My Familiar.

Why must a hero kill the Demon King? Besides, the Demon King is also a cute girl? Wouldn't it be nice to use hidden props to turn her into your familiar and let her help with laundry and cooking? I don't know who wrote the program by foot, but I actually succeeded, but there was a bug, a system error, and I did not return to the original world. Therefore, with the Demon King who became his familiar, the brave Aigen embarked on a two-week adventure under the HARD difficulty condition without system guidance. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.