Guang is a story about two brothers. The elder brother, Wen Guang is autistic. Wen Guang is often misunderstood. Above all, he suffers from attention deficiency disorder, struggles with social interaction, and has difficulty performing day to day obligations. He also has a secret passion. To make ends meet, Wen Guang is coerced by his younger brother into looking for a job to share his burden on meeting their monthly expenses. Throughout the film, we see Wen Guang searching for a job, his daily routines and his secret passion as he searches for the final glass that will bring him a simple, pure, hard earned, fleeting moment of joy.

患上自閉症的文光一直無法專注集中以及正常社交。雖然如此，弟弟卻一直設法讓文光外出工作幫補家裡生計。文光擁有一個秘密志願，一直希望可以找到那個可以帶給他純淨與歡樂的玻璃。