"Happy Together" portrays the daily life of the Man family, reflecting the living conditions of a typical Hong Kong family. For example, the family participates in property speculation and loses miserably, the wife works outside and causes dissatisfaction from her husband, the wife plans to invest in immigrating to a foreign country as a backup plan, middle-aged men having extramarital affairs, the wife's younger brother "Ah Chai" applies for public housing, the wife's shopping addiction, divorce between Zhu Zaibao and Dan Nao, the robbery of the Man family, Mr. Man's desire to return to mainland China for business, and Yue being forced by his mother to sell ginger as a street vendor. These were common events among Hong Kong people at the time, and the show brought these topics to television, resonating with the audience.

Orphan Ma Tianyou was raised by nuns in a Macau monastery, and grew up with Sister Connie, who knows the truth about his parents but kept it secret. At 19, Tianyou goes to HK to find his birth parents and ends up living with retired Dr. Fung. He meets the Wong family and falls in love with Ah Heung, but their relationship is complicated by their sibling-like bond. Back in Macau, Sister Connie reveals the painful truth that Tianyou's father is Fung's son, Fung Yue-lai, who had a complicated past with her and her friend who died giving birth to Tianyou. After struggling to accept his philandering father, Tianyou gradually reconciles with him.

Xing Feng is a top model with a passionate and carefree personality. She is only interested in Man Shi Hua, a man who matches her well and is a social celebrity. However, after a fight, Xing Feng meets Ye Jia Cheng, a design student and amateur photographer. They fall in love but their relationship is destroyed by Xing Feng's mother. Later, Man Shi Hua misunderstands Xing Feng's relationship with Ye Jia Cheng and seeks revenge. He distances himself from Xing Feng, leaving her heartbroken. Xing Feng moves in with Ye Jia Cheng and they become a couple. However, when the police investigate a case involving Man Shi Hua, he frames Ye Jia Cheng for it. Xing Feng confronts Man Shi Hua and agrees to spend the night with him in exchange for him dropping the charges against her boyfriend.