Weaving two stories set 30 years apart, First of May (五月一號) is about a middle-aged man looking back at his teenage years, dreaming of his first and possibly only love. At the center of the drama is Bai (Lyan Cheng, 程予希), a 17-year-old student living with her single mother, Wong Lei (Alyssa Chia, 賈靜雯), and her grandmother. Bai gradually falls for her admirer/stalker, Yeh (Anderson Cheng, 鄭暐達), who is always walking behind her and her best friend Wen Wen (Shao Yu-wei, 邵雨薇) wherever they go.