Su Tang, eighteen years old and the top science-track student in his province, is handed over by his stepfather to Ai Xian, the older sister who dislikes him most. Sharp-tongued and short-tempered, Ai Xian orders him to call her "Master," sleep in the spare room, and submit his schoolbag to random inspections. But when a rich second-generation heir falsely accuses him of stealing a card, she slaps the shopping mall manager to the ground and declares, "He's my little brother!" Also living with them is the gentle roommate Lin Yi, who cooks noodles with a fried egg and pretends to be Su Tang's girlfriend to chase away a domineering vocational-school girl. Then there's Bai Lu, a scatterbrained painter who mistakes lettuce for a crunchy snack but insists that Su Tang pretend to be her boyfriend to deal with her parents. Three older sisters and one younger brother. He thought he was merely living under someone else's roof, but instead became everyone's beloved. She thought she was taking in a burden, but ended up raising her strongest ally.