After his mother remarries, the sensitive and introverted Su Tang moves in with the Ai family, where he lives alongside Ai Xian, a cold and sharp-tongued campus beauty; Lin Yi, a charming and perceptive mature woman; and Bai Lu, an adorably absent-minded art enthusiast. Through a series of hilarious clashes and by facing troubles together, he sheds his timidity and gradually grows into a responsible young man. However, the appearance of a mysterious assassin uncovers an eighteen-year-old secret: his biological father is still alive. Determined to protect his older sisters, Su Tang resolutely embarks on an unknown adventure.