In his first life, Zhang Jingmo was betrayed by Lu Guijiu and imprisoned. After being reborn, he swore to make Lu Guijiu pay blood for blood. And so he was reborn, and Lu Guijiu did pay blood for blood, and then... he died. Once, twice, three times, four times—after countless rebirths, Zhang Jingmo finally discovered that being imprisoned by Lu Guijiu... was actually his best possible ending. And so—

Zhang Jingmo: "Please lock me in the dark room."

Lu Guijiu: "No imprisonment for you, my dear."

This is actually a pure story of mutual pining (lol)