Erza is likely to be a main female character as well. She is strong and has her own unique relationship with Natsu. In this fanfiction, her reaction to Natsu leaving would be quite significant. She might be torn between her loyalty to the guild and her feelings for Natsu.
Lucy is usually one of the main female characters. She has a deep bond with Natsu through their adventures together.
Another main female character could be Wendy. She looks up to Natsu and would be greatly affected by his departure. Her kind and gentle nature would add an interesting dynamic to the story, especially in the context of the harem situation where she might be more reserved in expressing her feelings compared to the others.
Gray would be shocked at first. He and Natsu have a long - standing rivalry - but also a deep friendship. He might initially be angry that Natsu would just leave like that, but then he would realize how much he'll miss him. He might also feel a sense of loss for the guild as a whole, since Natsu is such an important part of it.
In 'natsu leaves fairy tail harem fanfiction', a common storyline could be that Natsu leaves to seek his own power or identity outside of the guild and the harem. The female characters then form a sort of search party to find him. Along the way, they encounter different challenges that make them grow both as individuals and in their relationships with each other. This could also lead to some of them realizing that they don't just want Natsu back for the sake of the harem, but because they truly care about him as a person.
Lucy is definitely one of the most common. She has a close bond with Natsu from the start of the series. Erza is also often included. Her strong and confident personality makes her a great addition to the harem. Wendy could also be part of it. Despite her young age, she has a deep respect and admiration for Natsu.
It could be a group of rogue mages who have a vendetta against Natsu and Erza. They see the two leaving Fairy Tail as an opportunity to attack them when they are more vulnerable outside the protection of the guild.
Gray could be one. Since he and Natsu have a long - standing rivalry, Gray might try to bring Natsu back to Fairy Tail. He'd be conflicted between his annoyance with Natsu and his concern for his former guildmate.
There could be a mysterious old wizard who takes Natsu under his wing when he leaves Fairy Tail. This wizard might have knowledge of ancient magics that Natsu is eager to learn.
Typically, in 'natsu harem fairy tail fanfiction', there is a focus on Natsu having multiple female admirers or love interests. These female characters often come from the Fairy Tail guild. The stories usually involve a lot of interaction between Natsu and these girls, with elements of romance, friendship, and sometimes adventure.
Obviously, Natsu himself is a central character. He is the main attraction in the harem scenario. His fiery personality and powerful magic make him a key figure. Then there's Lucy. She is often included in the harem as she has a strong bond with Natsu in the original Fairy Tail series. Her celestial spirit magic also adds an interesting element to the fanfiction. Happy, the blue flying cat, is also popular. He can provide comic relief and also plays a role in the adventures, especially when it comes to helping the children in the story.
Seilah is also a main character in this context. She has her own set of powers and a rather complex personality in the Fairy Tail universe, which can be further explored in fanfiction.
One great 'Fairy Tail Natsu x Harem' fanfiction is 'A New Adventure'. It has an interesting plot where Natsu finds himself in various unexpected situations with the harem members. The character development is well - done, especially how Natsu's relationships with each of the harem characters evolve over time.