For a long time, Maiku Kamishiro has been trying to solve the mystery of his own past. He only has one clue: an old photo of a boy and a girl playing in a small pool in front of a blue house. Determined to find out the truth, he moves to the same location and becomes successful as a programmer. Suddenly, his peaceful life is disrupted by the arrival of two women with opposite personalities. They both have the same photo as evidence and claim to be his twin. Since there is no concrete proof to confirm either claim, Maiku decides to let them stay until the truth can be uncovered.