Rising Son is set during the Japanese invasion and occupation of Singapore between 1941 and 1945. 18 year-old Sunny (Tan Shou Chen) is enlisted as an ambulance orderly when the bombing starts, and does his best to protect his naive, but headstrong, younger sister Ruby (Seong Hui Xuan) from the horrific realities of war.
When the occupation begins, and Singapore becomes Syonan-To, the siblings meet a young Japanese army lawyer (Caleb Goh) who has moved into the house next door. An awkward friendship develops between the three in the years that follow, which affects their experiences of the war.