The main characters are Ace and Luffy. Ace, with his strong sense of justice and loyalty, and Luffy, with his boundless enthusiasm and dreams of becoming the Pirate King. Their relationship as brothers is a key aspect. Ace might take Luffy with him to teach him important things about the pirate world, like how to handle different situations, deal with powerful foes, and also to share some of the family secrets that he might know.
In this fanfiction, the two central characters are Ace and Luffy. Ace, being the older brother, is likely to be the more protective and guiding one. Luffy, on the other hand, is full of energy and curiosity, always ready for an adventure. Their different personalities will surely lead to many interesting events in the story.
In this kind of fanfiction, Ace might take Luffy on an adventure to find a hidden treasure. They could encounter various powerful enemies and strange islands along the way.
Obviously, Ace and Luffy's crew which includes Luffy himself, Zoro, Nami, Usopp, Sanji and others are the main characters.
Often, the Marines can be main antagonists. They see pirates as a threat, and with Ace and Luffy being pirates, they would be constantly on the Marines' radar. Marines like Akainu are especially dangerous, as his extreme sense of justice could lead to direct confrontations with the brothers.
In the 'Naruto Saves Luffy and Ace Fanfiction', the main villains might include the World Government from One Piece. They have a lot of power and resources and are often against pirates. Also, there could be some rogue ninjas from Naruto's universe who are attracted by the chaos and want to take advantage of the situation. These villains would pose a great threat to Naruto's mission of saving Luffy and Ace, making the story full of tension and conflict.
Obviously, Ace and Luffy are the most popular. But other characters like Zoro from Luffy's crew are also often included. On the marine side, characters like Smoker are quite popular as he has a sort of grudging respect for Luffy. Also, Akainu is often included as the big bad marine that Ace and Luffy have to face off against.
Well, 'Luffy and Ace: Unbreakable Ties' is a fanfiction that I really like. It focuses on their childhood memories and how those shaped their relationship as they grew up. There's also 'Ace and Luffy's Great Escape' which is full of action. It shows their cleverness in getting out of difficult situations. 'Luffy and Ace: The True Friendship' is a must - read too. It simply and effectively shows the depth of their friendship.
Whitebeard is another character that could be important in these fanfictions. As Ace's adoptive father, he plays a significant role in Ace's life. Fanfictions might explore how Whitebeard's influence on Ace affects his relationship with Luffy, like how Whitebeard's values of family are passed on to Ace and then reflected in how he treats Luffy.
In most Naruto Ace fanfiction, Naruto and Ace are front and center. But sometimes, other characters from both universes might also play important roles. For instance, Sakura could be involved if the story is set in the Naruto world and she has to deal with the arrival of Ace. Or Luffy might be mentioned in relation to Ace's backstory and how it affects his relationship with Naruto.
One great 'Ace Protective of Luffy' fanfiction is 'The Unbreakable Bond'. In this fic, Ace is always on high alert to protect Luffy from any threats in the New World. He uses his fire powers in really creative ways to fend off enemies.
Well, one characteristic could be the focus on a more 'romantic' or 'intimate' relationship between Luffy and Ace, which is often not in line with the original platonic nature of their bond in the source material. However, this is a very controversial aspect as it goes against the typical portrayal of their brotherly relationship.