Well, it could be that Naruto's blindness is related to some ancient prophecy. In the fanfiction, it might be that his blindness is a sign that he is the chosen one to face a certain evil. Since he is blind, he has to learn to see the world in a different way, which gives him a unique perspective. He may start to have strange visions or dreams that guide him in his journey. And his friends in Konoha initially think he is just being strange, but later realize the truth and help him embrace his role as the one with this special 'blind' condition to save the world.
One possible plotline could be that Naruto has been hiding his blindness all along to protect his friends. He might have developed special techniques to compensate for his lack of sight, like relying more on his other senses such as smell and hearing. For example, he could use his sense of smell to detect enemies' movements and positions, similar to how he uses it to find Sasuke in the original series. Another idea is that his blindness is a result of some hidden power or curse, and as the story unfolds, he has to find a way to either overcome it or use it to his advantage.
One possible plotline could be that Naruto discovers a hidden vampire world while on a mission. Maybe he stumbles upon a vampire lair and has to figure out how to deal with these new, powerful creatures. He could be intrigued by their powers and try to learn from them while also keeping his own ninja village safe from any vampire threats.
One storyline could be Naruto gradually losing his sight over time but hiding it because he doesn't want to worry his friends or seem weak. He could struggle with simple tasks like reading scrolls or finding his way around Konoha without making it obvious.
One possible plotline could be that they got married to form an alliance between two powerful factions secretly. Another could be that they fell in love while on a secret mission together that no one else knew about. Maybe Itachi was on a mission to protect Naruto from afar and they developed feelings over time.
One possible plotline could be the discovery of her secret marriage. Maybe a nosy villager starts to suspect something and begins to dig deeper. This could lead to a series of events where Fem Naruto has to work hard to cover her tracks and protect her relationship.
One possible plotline could be that Jaune has been hiding his Faunus identity to avoid discrimination. As the story progresses, his secret might be revealed during a crucial event, like a battle where his Faunus abilities give him an edge.
A 'Naruto Secretly Blind' fanfiction could be centered around Naruto's secret being a major plot device. It could be that an enemy discovers his blindness and tries to use it against him. Naruto then has to find new ways to fight and protect the village. His blindness could also be the result of a powerful jutsu gone wrong, or perhaps it was a sacrifice he made for the greater good without anyone knowing.
One possible plotline could be that they got engaged during a dangerous adventure. Maybe they were trapped somewhere and made a pact to get engaged if they survived. And then they keep it a secret because they know their friends and families might not approve. For example, Ron might be really shocked and angry at first if he found out.
One possible plotline could be that Ruby discovers her hidden princess heritage and has to balance her normal Huntsman duties with the newfound responsibilities of royalty. Maybe she has to attend grand balls and diplomatic meetings while still trying to fight Grimm. Another could be that she has a secret princess identity that she uses to infiltrate an enemy kingdom or group, using her charm and skills as Ruby as well as her new royal persona.
One possible plotline could be Timmy struggling to keep her secret while dealing with her Fairy Godparents. Maybe she's afraid they'll react differently if they find out she's a girl. For example, she might worry that they'll start treating her like a princess instead of a regular kid with wishes.
One possible plotline could be that they discover they have more in common than they thought. Maybe they start working together on a project in the wizarding world, like researching a long - forgotten magic. As they spend time together, they realize their feelings for each other have changed from hatred to love. To avoid the chaos that would ensue from their families and friends' reactions, they decide to marry secretly. Another idea is that they are forced into a situation where they have to pretend to be married for some magical reason, like protecting a powerful spell or object. During this time, they start to really fall for each other and end up making it a real, secret marriage.