LONG LONG TIME AGO follows the trials and tribulations of a family from 1965 to the early 1970s. Their journey through the years from their humble kampong to a modern HDB flat, runs in parallel with Singapore's early growth. On 9 August 1965, Zhao Di (Aileen Tan) is driven from her husband's home. The same night, she gives birth to twins, Shun Fatt and Su-mei. Unfortunately, Su-mei is born with two moles on her face - a sign of misfortune for the family. Under her family's pressure, Zhao Di is forced to give Su-mei away. This is only the first of many challenges, but with Zhao Di's indomitable spirit, the family perseveres to make a better life for themselves. Over the years, the family witnesses every step of the nation's growth.

In an alternate timeline, Ken, Lobang and Wayang King are transferred to the Naval Diving Unit (NDU) and have to overcome obstacles and personal issues to grow as people.