Lee Su-jin's joyless marriage to Kwon Do-hun -- with whom she was once deeply in love -- reaches a breaking point when he refuses to have a baby.
While Do-hun hides secrets from Su-jin, she considers an unorthodox idea to try and force him into a speedy divorce.
Brian Jeong and Son Ye-rim cook up a scenario for Su-jin's divorce project, and Do-hun spends time with his mother-in-law.
Moving her plan forward, Su-jin gets Do-hun to agree on a fishing trip with her. Brian stands up Ye-rim for dinner.
With his symptoms accelerating, Do-hun knows he must give Su-jin what she wants -- or risk her finding out about his illness.
Forgetting he needs to stay away, Do-hun heads to Kwon A-ram's kindergarten. Mun Kyeong-hun carves out a place in Su-jin's life.
Su-jin worries that Do-hun has reappeared to take A-ram away from her. Meanwhile, Brian and Ye-rim come across each other on a film set.
For the first time in years, Do-hun and Su-jin come face-to-face. Choe Hang-seo and Baek Su-a throw a wedding celebration. Brian meets Ye-rim's fiancé.
Do-hun's proposal for launching a sugar-free chocolate bar falls through. Su-jin locks herself away in her apartment, worrying her friends.
Jo Mi-kyeong and her mother disapprove, but Su-jin decides she wants to be by Do-hun's side -- and brings A-ram to him.
Do-hun remembers how he fell in love with Su-jin, who packs up his bags to take him back to the house. Ye-rim makes her choice about Brian.
Losing more of himself each day, Do-hun works on creating good memories with A-ram, and Brian offers to film a video to preserve them.
When Do-hun's condition reaches new lows, Su-jin recounts their story to him. The patent for his chocolate bar is found to have been stolen.
Su-jin plays along with Do-hun, who thinks he is in his 20s -- but runs into trouble when he gets jealous of Kyeong-hun.
Do-hun's Alzheimer's disease progresses, erasing even Hang-seo. A-ram wonders why they can't play together -- and Su-jin must explain why.
To A-ram's delight, Do-hun attends her kindergarten event, and the family goes on its first vacation. The chocolate bar relaunches under a new name.
