Cha Joo-hyuk is a bank worker who has been married to Seo Woo-jin for five years. Due to financial pressures and work stress, Joo-hyuk resents his wife, while Woo-jin suffers from working-mother burnout and sudden anger outbursts, leading to a miserable marriage where they barely speak to each other. One day, a mysterious encounter grants Joo-hyuk the extraordinary opportunity to travel back in time to the exact day he made a fateful choice ten years ago. Choosing differently alters his present entirely: he wakes up wealthy, married to his college crush Lee Hye-won, and living a completely different life where he never met Woo-jin. However, fate has other plans when he transfers to a new bank branch and discovers that Woo-jin is now his upbeat, single coworker. As memories of their past life begin to resurface and he observes Woo-jin's struggles in this alternate reality, Joo-hyuk is forced to confront his own shortcomings and examine what truly makes a relationship meaningful.