Main character is a friend of Agawa family where three sisters reside. He is good at household activities, so he does the cooking, washing and cleaning there. When protagonist descends to a basement of the house he used to live, he finds strange paintings and treasures. He learns that he is supposed to be a phantom thief to protect the world peace. The Earth is in danger unless he realizes scenes from the paintings. He continues to do the chores during the day, but at night starts to practice harassment with the Agawa family sisters.

[From vndbreview]