On Zhu Qing'an's arranged wedding day to Yuan Zhong, best man Si Yu falls in love with her at first sight. When Yuan Zhong panics over a fake pregnancy text from his ex, he begs his lookalike friend Si Yu to wear a mask and stand in for the ceremony. Pretending to hesitate, Si Yu secretly detains Yuan Zhong, then approaches Qing'an, exposing Yuan Zhong's flaws while passionately pitching himself as her replacement groom. Seeing through his scheme, Qing'an plays along and agrees to the swap. Si Yu swiftly updates the wedding items, publicly marries Qing'an, and rushes her into officially registering their marriage.At home, Si Yu turns into a clingy, overly protective husband. He plays the vulnerable victim around any rival, cooking, kissing, and demanding all her attention—subtly isolating anyone approaching her. Meanwhile, the cool-headed Qing'an controls the entire board, seeing through his manipulative "green-tea" tricks and playfully teasing him back.Desperate to ruin them, Yuan Zhong leaks a maliciously edited recording showing Si Yu's scheme to instigate his flight. Pretending to be heartbroken over his calculation, Qing'an demands a divorce. Panicked, Si Yu gets drunk, tearfully confessing all his dark motives and deep obsession. In a car confrontation, Qing'an reveals her ultimate twist: she overheard his initial wedding plot all along, and her anger was merely a test. Knowing his devotion is genuine, they reconcile.After exposing that the ex's baby wasn't Yuan Zhong's, Si Yu traps him in his own deceit, wiping out all threats. Fully equal in wit and love, Si Yu embraces a lifetime of devotion alongside Qing'an.