Definitely Lucy. She and Natsu have a special bond, and she'd be right by his side, sharing her wisdom and helping with whatever Natsu needs. Then there's Happy. Natsu's loyal Exceed friend would be constantly around, providing comic relief but also being a source of emotional support. And don't forget about Makarov. As the guild master, he might offer his guidance and protection to Natsu during this unusual situation.
Lucy is often a common supporting character. She's Natsu's close friend and partner in many adventures in the Fairy Tail world. She would likely be there to support Natsu during his pregnancy, offering her friendship and maybe some practical help. Gray is another one. Despite their rivalries, he would probably step up to support Natsu. And of course, Erza. With her strong and protective nature, she would be a great source of support for Natsu during this time.
Happy is almost always there. He's Natsu's loyal sidekick and provides comic relief as well as support during training. Lucy also frequently appears. She might offer some strategic advice or just be there to cheer Natsu on. Erza is another common character. Given her strong and strict nature, she could be the one pushing Natsu to his limits during training.
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.
Well, first off, Happy has to be a really popular supporting character. Happy is Natsu's best friend and sidekick. In stories about Natsu growing up, Happy is there every step of the way, providing comic relief and also being a source of motivation for Natsu. Another popular one is Wendy. As a young and talented mage, she can be a symbol of new hope and growth in the guild. In fanfictions, she might team up with Natsu more often as he grows, and they can learn from each other. And then there's Makarov. The guild master is an important figure. He has a lot of wisdom to offer Natsu as he grows, and his leadership and care for the guild members, including Natsu, are often explored in these fanfictions.
Erza is frequently paired with Natsu in these fanfictions. Given her strong and leadership - like qualities, she can take charge in agent - related situations, and Natsu can be the more impulsive force. Their interactions can range from Erza scolding Natsu for his reckless actions to them having deep conversations about their responsibilities as agents. Wendy is also a character that can be paired with Natsu. Her healing magic can be crucial during dangerous agent missions, and she looks up to Natsu, which can create a sweet and protective relationship in the fanfiction.
There are several important supporting characters. Levy is one. Her knowledge of books and magic could assist Natsu in his rule, especially when it comes to understanding the history and secrets of the academy. Cana could be important too. With her card magic, she might be involved in predicting events or providing strategic advice. And Loke, as a powerful celestial spirit, could be a valuable ally for Natsu when facing tough challenges within the academy.
Erza Scarlet is frequently seen as a supporting character. Her strong leadership and combat skills can be very helpful in battles that the Lightning Dragon Slayer is involved in. Wendy Marvell might also be there. As a sky dragon slayer, she has a different perspective on dragon slayer magic which can be useful for the Lightning Dragon Slayer. Happy, the flying cat, can provide comical relief and also assist in transportation or scouting in some fanfictions.
Mirajane is a popular choice too. She has a mysterious side to her, and in the fanfictions, she could use her unique abilities to help Natsu or be involved in the events that the Fairy Tail members are watching. Also, Laxus might be included. His powerful magic and complex character can add depth to the fanfiction stories, especially when his relationship with Natsu and the rest of the guild is explored.
Definitely Lucy. Their bond is so strong that if there were any cracks in it, like if Lucy started distancing herself from Natsu without a clear reason, it would be devastating for him. Gray is also a candidate. They've been through so much together, and if Gray were to say or do something really hurtful, like blaming Natsu for a big mistake that wasn't his fault, it could lead to heartbreak. Juvia might be involved too. If she tried to keep Lucy away from Natsu for her own love for Gray, it could cause problems for Natsu and lead to his heartbreak.
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.
Obviously, Natsu is a very popular character as it's in the title. He is often the center of many fanfictions. Lucy is also quite popular as she has a close relationship with Natsu in the original series. Their dynamic often plays a big part in fanfictions.