I don't have enough context to determine exactly who 'garp' is. It could be a newly created character by the fanfic writer, or it might be a character from a relatively unknown story that is being incorporated into the 'ace fanfic'.
The following conclusions were made: the old five unique skills referred to the Eastern Evil, Western Poison, Southern Emperor, Northern Beggar, and Middle Divine Power, which were decided in Huashan, while the new five unique skills referred to the Eastern Evil, Western Madness, Southern Monk, Northern Swordsman, and Middle Wantong, which were decided in Zhonghua Mountain. The two Sword Seminars at Huashan were about 60 years apart, so the strength of the old Five Uniques and the new Five Uniques could not be exactly the same. According to the information provided, it was impossible to accurately answer the gap between the old Five Uniques and the new Five Uniques, and who was more powerful. This was because the information did not provide a direct comparison or ranking of their strength. Therefore, he could not give a definite answer to the question of the old Five Uniques versus the new Five Uniques.
One common theme is the clash of ideologies. Akainu has a very strict and uncompromising view of justice in his original story, while Naruto has a more forgiving and rehabilitative view. So when they interact in fanfiction, this clash often forms a central theme.
I'm not entirely sure specifically what 'garp save ace fanfiction' is about without more context. It could potentially be a fan - made story in which Garp tries to save Ace within the context of a particular fictional universe, perhaps related to One Piece.
Character development is key. Fanfictions explore how Ace and Luffy grow under Garp's influence. Maybe Luffy becomes more disciplined in some stories, or Ace learns to be more open - hearted, all thanks to their interactions with Garp and each other.