Aki survives in the manga. The plot doesn't lead to his death. Maybe there were some tense moments that made you think that, but ultimately, he makes it through.
Sora is likely a character created within the fanfic world. He could be a powerful shinobi with unique abilities that Naruto can learn from. Maybe he has a special chakra nature or some extraordinary combat skills.
Sure, Masamune and Aki end up together in the manga. The author crafted a beautiful love story where their connection deepened over time, and ultimately they found their happily ever after.
One common theme is friendship. Yusei and the other characters often form strong bonds in these fanfics. Another theme could be self - discovery. As the story progresses, the characters might learn more about themselves. Also, adventure is quite popular, with the characters going on various quests or facing challenges.
Another theme is growth. As the story progresses, both Shima and Aki may grow as characters. For example, they could learn important life lessons from their interactions with each other. In some fanfictions, they overcome personal weaknesses with the help of their relationship.
Often, there are themes of emotional connection between Yusei and Aki. The fanfiction might explore how they support each other through difficult times, and then build on that with the 'lemon' aspect which adds a layer of physical and sexual tension. Another theme could be the growth of their characters within the relationship, as they face challenges together and become closer both emotionally and physically.
Well, it depends on how you look at it. Technically, in official Kingdom Hearts content, Sora is a key character. But in the realm of fanfiction, many writers take the essence of Sora and create their own unique stories that are not part of the official canon but are still inspired by the Kingdom Hearts universe. So, in that sense, he can be considered as a major element in Kingdom Hearts fanfiction.