One possible plot could be that Bulma might be jealous of the relationship Goku and Chi - Chi have. Maybe she sees how much Goku has changed since being with Chi - Chi and she misses the old, carefree Goku. So, she tries to create misunderstandings between them by, for example, making it seem like Goku is more interested in training with her than spending time with Chi - Chi.
In the fanfic, it could be that Bulma has some secret plan that she thinks requires Goku to be single. Maybe she wants to use Goku in some sort of experiment or mission that she believes he can't do while being in a relationship. So, she starts to spread false rumors about Chi - Chi not being good enough for Goku or tries to make Goku think that Chi - Chi doesn't understand his true passion for fighting.
Well, perhaps in the fanfic, Bulma believes that Goku is too powerful for Chi - Chi to handle and she thinks Chi - Chi is holding Goku back from reaching his full potential as a fighter. So, Bulma tries to break them up by showing Goku all the great things he could achieve if he was single again, like exploring new planets and training with stronger opponents.
Goku would probably be really confused. He loves Chi - Chi and their family, and he might not understand why Bulma would want to break them up. He might just tell Bulma straight that he's happy with his life as it is. Chi - Chi, on the other hand, would be furious. She's very protective of her family and her relationship with Goku, and she'd likely give Bulma a piece of her mind.
Chi - Chi would likely be very hurt at first. But then she would get angry and start thinking of ways to prove to Goku that their relationship is strong. She might cook his favorite meals and remind him of all the good times they've had together, while also giving Bulma a piece of her mind.
One possible motive could be that Bulma is worried about Goku's safety. Since he's constantly getting into dangerous battles, she might think that if he's not tied down to Chi - Chi, he could be more focused on self - preservation. Maybe she feels that Chi - Chi's family demands on Goku are a distraction and could lead to his downfall in a fight.
One idea could be that Goku forgets their anniversary. Chi Chi is initially angry but then decides to use this one - week period to remind Goku of their relationship. She sets up various challenges and tasks for Goku related to their past memories together. As Goku goes through these, he rediscovers his love for Chi Chi in a deeper way.
Well, in a one - week fanfic about Chi Chi and Goku, they might go on a training adventure together. Chi Chi could be trying to keep up with Goku's intense training regime, and there could be some cute and funny moments as she struggles. Maybe they also take some time to just relax and have a family picnic with Gohan. It would be a story full of action, family love, and the unique dynamic between these two Dragon Ball characters.
I'm not sure if there is an actual fanfic with that exact plot. Fanfic topics can vary widely, but this seems like a rather unfaithful and out - of - character concept considering Chi Chi's strong bond with Goku in the original series.
Love and family are very common themes. Their relationship as husband and wife, and as parents to Gohan and other children is often explored.
Maybe in this fanfiction, Goku realizes that he and Chi - Chi have very different personalities. Chi - Chi is often more concerned with family and a stable life, while Goku is a free - spirited adventurer. This clash of values could lead him to decide not to marry her. For example, Chi - Chi may want Goku to stay at home and help raise Gohan, but Goku is eager to explore new planets and fight powerful enemies.
In a fanfiction like this, perhaps Bardock is on a mission in the afterlife and it leads him to cross paths with Goku and Chi - Chi. Bardock could test Chi - Chi's strength and worthiness to be with his son. Chi - Chi would rise to the challenge, showing her determination. Goku would be in the middle, trying to make sure his father respects his wife. And in the end, Bardock could give his blessing to their relationship, seeing how happy they are together and how Chi - Chi has made Goku a better person in many ways.
One reason could be his pursuit of stronger opponents. Goku is always eager to test his strength and find new challenges. In fanfiction, this might lead him to leave Chi - Chi to travel the universe in search of the toughest foes. He might feel that staying at home with his family restricts his growth as a fighter.