One possibility is that they find an abandoned place full of ancient magic. Natsu, with his dragon - slayer powers, and Lisanna, with her unique skills, might start to unlock the secrets of this place. They could learn new spells or techniques that would not only help them get back but also make them stronger in the long run. This could also be a time for their relationship to grow, as they depend on each other in this strange situation.
In this kind of fanfiction, they might face various challenges. Maybe they'll have to find their way back on their own. They could encounter dangerous magical creatures and have to rely on their own skills and the bond between them to survive.
In this fanfiction, they might have to face a series of challenges alone. Maybe they'll encounter powerful enemies that they have to defeat without the help of their usual comrades. They could also discover new powers or abilities within themselves during this time of being left behind.
The main characters are clearly Natsu and Lisanna. Natsu is a well - known character with his fiery personality and powerful dragon - slayer magic. Lisanna is also important, she has her own set of skills and a unique relationship with Natsu.
Perhaps they get left back because of some external factors. Say, an enemy attacked their guild right before an important exam. Lisanna and Natsu were so busy fighting off the enemy and protecting their guildmates that they missed out on crucial study time. They might have also gotten injured during the battle, which further hindered their performance in the assessment, causing them to be held back.
Lisanna might face a lot of backlash from the guild. Her friends could be disappointed in her and might not trust her as much. She could lose her standing in the guild and have to work hard to regain people's respect.
Their relationship with the guild leaders could become strained. The leaders might see them as irresponsible for getting left back. However, as time passes, Lisanna and Natsu could prove themselves in other ways, like taking on extra tasks around the guild to show their dedication. This could gradually change the leaders' perception of them and strengthen their relationship in the long run.
It's Natsu and Erza. Natsu, the energetic dragon slayer, is always ready for a fight and has a great sense of loyalty towards his friends. Erza, with her strict yet caring nature, is a force to be reckoned with. In this fanfiction, their individual skills and personalities will likely be explored more deeply as they are left behind.
A plot could be that Natsu and Lisanna have been longing for a baby. They go through a magical ritual in their guild to increase their chances of having a child. Once Lisanna becomes pregnant, the whole guild gets involved. Everyone is excited and offers their help. Natsu becomes super protective of Lisanna and the unborn baby. There could be a sub - plot where an enemy tries to target Lisanna because of the powerful baby she is carrying, and Natsu has to fight to keep them safe.
Another aspect could be their relationship growth within the marriage. They might have deep conversations about their past traumas and how they've overcome them. It could also show how their love has changed and become even stronger over time, with little romantic moments like stargazing together on the rooftop of their home.
Well, perhaps in the fanfiction, Natsu and Lisanna discover they're having a baby unexpectedly. They then have to adjust their lives as members of Fairy Tail. Lisanna might worry about how her pregnancy will affect her ability to go on missions. Natsu, on the other hand, vows to be the best father and to keep his family safe from any threats that may come their way, be it from dark guilds or other magical creatures.
One possible plot could be that they discover the pregnancy and start preparing for the new arrival. They might face challenges like how to balance their duties in the guild with the upcoming parenthood. Natsu could be overly excited but also a bit clueless at first.