My Sweet Battle Maids

After saving an old man from a monster attack, the old man blesses the protagonist with a fortune beyond belief. That fortune is a massive massion with eight maids at his command that will serve him. The protagonist is grateful for this fortune, but before he can become their master he has to prove himself to the maids. How must he prove himself? By defeating all eight maids. Only then will they recognize him as their master. The eight maids may look cute but they are insanely powerful, only having one previous master in their history of being maids...the old man. The protagonist seems to want to take on this challenge as he's never backed away from a challenge before in his lifetime. This will be the start of a new chapter in his life.