At the end of the Southern Dynasties, Emperor Wen of the Sui Dynasty, Yang Jian, conquered the neighboring states of Southern Chen and Northern Qi, establishing the Sui Dynasty. At that time, several small states coexisted in southern China, one of which was the Chen Kingdom, whose capital was Jiankang (present-day Nanjing). The Sui Dynasty had long coveted these southern states and was always prepared to unify the entire country.
Xu Deyan served as an attendant to Chen Shubao, the emperor of the Chen Kingdom. He married the emperor's younger sister, Princess Lechang, and the two deeply loved and cherished each other. However, the Chen court was corrupt, and the unification of the realm was an inevitable trend. Xu Deyan foresaw that one day their country would face destruction, and thus he was filled with anxiety.
One day, with a deeply troubled expression, he said to his wife: "War may break out soon. When that happens, I will have to protect the emperor, and we will be forcibly separated. But as long as we are alive, there will always be a chance to meet again. We should leave behind a token now, as proof for our future reunion." Thereupon, Xu Deyan took a round bronze mirror, broke it in two, kept one half for himself, and gave the other half to his wife. He told her to preserve it carefully and said: "If we become separated, on the fifteenth day of the first lunar month each year, have someone take this half-mirror to the marketplace to sell. As long as I am still alive, I will certainly go there to inquire, and using my half-mirror as proof, I will find a way to reunite with you."
Soon afterward, Emperor Wen of Sui, Yang Jian, who had already unified northern China, indeed launched an attack on Jiankang, the capital of the Chen Kingdom. The small Chen state was quickly destroyed, its king was killed, and Xu Deyan was forced to flee into exile. Emperor Wen rewarded those who had contributed to the conquest of Chen, and the captured Princess Lechang was granted as a concubine to the minister Yang Su.
The exiled Xu Deyan learned that his wife had arrived in Daxing (present-day Xi'an, Shaanxi Province), the capital of the Sui Dynasty. He hurried there, covered in dust from his long journey, to search for her whereabouts. Whenever night fell and all was quiet, he would take out his half of the mirror and recall the happy times he had shared with his wife. Meanwhile, Princess Lechang, though living a life of luxury and elegance in Yang Su's residence, constantly thought of her husband in her heart and often gently touched her half of the mirror, reminiscing about the past.