One common theme is longing. The children or family members left behind constantly long for the mom's presence, like missing her physical hugs, kisses, and the warmth she brings. Another theme is the sense of loss. Even if the mom is away temporarily, there is a feeling of something missing in their daily lives.
Another theme can be the search for justice. As the story progresses, there is often a drive to find out who is responsible for the girl's disappearance and to make them pay. In 'Gone Girl', there is a complex web of lies and deceptions that need to be unraveled in order to find the truth about the missing woman and to hold the right people accountable.
Love is a very common theme. Moms often tell stories that involve love between family members or friends in bedtime stories. For example, a story about siblings who help each other out in a difficult situation shows love.
One common theme is guilt. A mother in such a situation often feels guilty for betraying the family values she is supposed to uphold. Another theme is secrecy. She has to keep her relationship as a mistress hidden from her children and others. And there's also the theme of self - discovery. Through this complex situation, she may come to realize what she truly values in life.
One common theme is mystery. Since it involves something 'missing' from the Mist, there's often a sense of intrigue about what happened. Another could be adventure, as characters go on a quest to find out what's missing.
Power and growth are also frequent themes. Away from her normal support system, Sakura has to develop new skills and become stronger. For instance, she might learn new jutsu or develop better combat strategies. It's about her evolving into a more formidable and self - reliant character.
Love is a very common theme. It could be the deepening of Bella and Edward's love, or the unrequited love of some secondary characters. Another theme is mystery. Since these are filling in the missing moments, there's often an element of mystery about what really happened during those times. For example, what was Edward really doing when he disappeared in 'New Moon'?
Isolation can be a theme too. In some cases, the missing person may have been isolated before disappearing, or the people left behind may feel isolated in their search for answers. In 'Gone Girl', both Amy and Nick were in a way isolated in their relationship which contributed to the events leading to her disappearance.
Isolation is a common theme. Since they are missing - nins, they are often alone and have to fend for themselves. Another theme is redemption. Many of these fanfics explore the idea of the missing nin trying to make up for their past mistakes.
Another theme is deception. Often, the people around the missing person are not as they seem. In 'The Girl on the Train', the narrator's unreliability shows how deception can play a big role in a missing persons story. People may be hiding secrets or lying about their relationship with the missing person.
One common theme is redemption. Since Naruto is a missing nin, often the stories explore his path to redeem himself while building his harem. Another theme is power. His new status as a missing nin might give him different powers or ways to use his existing powers in the context of the harem.