Namgung and Mi-do first met at the age of seven and began dating at twenty-six. Now in their tenth year together, the love they once believed would last forever begins to buckle under the weight of time. As their relationship changes, they are forced to confront the realities of love and life.

After ten years together, Mi-do and Namgung are struggling with their break up. Not even a romantic couples event can rekindle the spark between them, yet memories of the love they once shared keep pulling them back.

Namgung and Mi-do announce their marriage to their families and try to rekindle the spark between them. Mi-do's decision to step down as director puts her at odds with Tae-seung, while Namgung repeatedly clashes with Su-a as she investigates a sweet potato corruption scandal. As they spend more time with other people, Namgung and Mi-do begin to question whether their relationship can survive.

As news of the season's first snowfall spreads, Namgung and Su-a's shared past comes to light. Mi-do accepts Tae-seung's offer to return to directing, while Namgung refuses to help Su-a investigate a sweet potato corruption scandal. The four find themselves swept up in a whirlwind of complicated feelings.

Mi-do is shocked after waking up at Tae-seung's office. Meanwhile, Namgung notices a mysterious caller on Mi-do's phone and becomes uneasy. As always, the two pretend everything is fine for each other's sake. But the more they try to protect the relationship, the deeper their secrets become.

Mi-do deeply regrets what happened that day. Meanwhile, Namgung plans something to cheer her up. But unexpected visitors at his workplace push things in an unforeseen direction.

Namgung learns the truth about what happened that day, and the deep trust between the couple begins to unravel. Meanwhile, pressured by Ju-hyeok, Tae-seung makes an unexpected decision as his feelings for Mi-do deepen. At the same time, Su-a relentlessly pursues Namgung while investigating the sweet potato corruption scandal.

Namgung and Mi-do confront emotions they have long suppressed for each other's sake. As their pain pulls them in different directions, they come up with a bold proposal that could upend their relationship.