It could be a story about a secret and intimate relationship. Maybe the two characters are in a situation where they can only show their closeness behind closed doors, and the act of holding hands is a symbol of their deep connection.
Maybe it's about two original characters created by the fanfic author. One could be a shy and reserved person, and the other a more confident one. They find solace and a special connection when they are alone behind closed doors, and holding hands is their way of expressing their feelings for each other. The author might have created them to explore themes of introversion, extroversion, and how different personalities can come together in a relationship.
I'm not entirely sure as it depends on the specific fanfic. However, usually, the main characters are likely to be those who are most relevant to the central story or the ones that the plot revolves around.
One interesting plot could be the exploration of the characters' hidden pasts that are gradually revealed within the closed - door settings. It might add depth to their relationships.
The phrase 'behind closed doors' often implies secrecy or privacy. The full story could be about a confidential business deal. For example, two companies might be negotiating a merger behind closed doors. They don't want their competitors to know the details of their discussions, such as the price they are willing to pay or the terms they are offering. This secrecy helps them gain an advantage in the market.
Once, there was an old, dilapidated house. Behind its closed doors, a family had once lived. Late at night, strange noises could be heard. It was said that a dark figure roamed the halls. A young girl who used to live there disappeared mysteriously. People believe her spirit is still trapped, and at midnight, if you listen closely behind those closed doors, you can hear her faint sobs.
I haven't read this novel specifically, but generally, novels titled like this might deal with secrets, hidden lives or events that occur within private spaces. It could be about a family's hidden turmoil, a mystery involving a particular building's inhabitants, or perhaps a character's double life that is only revealed when the doors are closed.
Well, Naruto is almost surely one of the main characters since it's a Naruto fanfic. He might be the central focus as he usually is in most Naruto - related stories.