An open - ended ending can be interesting. Leave the reader with a question or a sense of mystery. For instance, a character discovers a strange object and at the end, they're just starting to figure out what it might be, leaving the reader to wonder what will happen next.
You could end the story with a mystery. Say, the characters find a strange object that has some symbols on it that no one can understand. The open end then allows the reader to wonder what the object is and what it might mean for the story. It could be a key to a hidden treasure or something more sinister like a cursed item.
One idea could be to provide a satisfying resolution to all the main plotlines. Make sure the characters' arcs are completed and their goals are either achieved or there's a clear reason why they weren't.
A cool concept for a 'Fairy Tail End' fanfiction would be to have a time - travel plot. The characters could go back in time to prevent a great tragedy that was hinted at in the original series. This would involve them interacting with their younger selves and changing the course of history in the Fairy Tail world. It would also be interesting to see how they deal with the knowledge they have from the future.
One idea could be to explore a scenario where friends turn on each other due to a misunderstanding over a valuable heirloom. Maybe one friend was entrusted with it for safekeeping but lost it, and the others think it was stolen on purpose.
Well, in some fanfictions of 'they both die at the end', the focus might be on how they make the most of their last day. It could involve them doing things they were always too scared to do, like confessing their true feelings to someone. They might also try to right some wrongs from their past. For example, if they had a falling - out with a friend, they would reach out and make amends. And the beauty of it is that it shows the power of self - realization and growth even in the face of death.
Another idea is a crossover with a superhero series. The seraphs with their powers could team up with superheroes. They could work together to fight a common enemy that is threatening both their worlds. This would bring in a mix of superpowers and different combat styles.
Often, a recurring symbol or motif works. Say, a specific object that appears at the beginning and plays a crucial role at the end. It ties the two parts together. Also, a promise made at the start and fulfilled in the end is a powerful connection.
An interesting plot could revolve around an OC who is an amnesiac. They wake up in the middle of the post - apocalyptic world of 'Seraph of the End' with no memory of who they are or where they came from. As they try to piece together their past, they discover that they have a special connection to both the humans and the vampires. Maybe they were part of an experiment in the past that gave them unique abilities. Their journey to recover their memory and understand their true nature could be full of twists and turns, and they might end up being the key to peace between the two warring factions.
One idea could be that End and Lucy are from different worlds. End is from a dark, magical realm and Lucy is from a more normal human world. They accidentally cross paths when a portal opens between their worlds. End is initially seen as a threat but as they interact, they start to understand each other and form an unlikely alliance against a common enemy that wants to destroy both of their worlds.
Well, a great plot idea could be a love triangle that unfolds as the story progresses towards the end of the road. For example, two characters both fall in love with the main character, and this creates a lot of tension and drama. Also, it could be about a mystery that lies at the end of the road. The characters are on a journey to solve this mystery, like who is the real villain behind all the strange happenings that lead to the end - of - the - road situation.