Maiku Kamishiro has long been haunted by the enigma of his lineage. Armed with just an old photograph depicting two youngsters frolicking by a blue abode, he relocates to this very house in pursuit of his roots, leading a mundane existence as a programmer. However, tranquility shatters when a pair of divergent young women appear at his doorstep, each brandishing the same image and asserting to be his twin sibling. With no definitive means to establish kinship, Maiku opts to accommodate both girls under his roof until the truth unravels.