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.
Well, in the Kanade Tachibana visual novel, she could be special due to her relationships with other characters. Her interactions, whether they are friendships or something more complex like a romantic interest, play a big role in making her unique. For example, the way she communicates and how she grows and changes throughout the story because of these relationships is really interesting.
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.
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.
I don't have direct access to yusei and aki lemon fanfiction. But you can start by looking at the top - rated or most - reviewed stories on fanfiction platforms. Also, consider the tags and summaries provided. If you like a particular author's writing style from other fanfictions, check if they have written anything about yusei and aki. This way, you might be able to find some great fanfiction.
The relationship between Endou and Aki has potential for a lot of emotional depth. Endou's passionate and determined personality paired with Aki's intelligence and supportiveness can create interesting storylines. Fanfics can explore their relationship development, from friends to something more, which is always engaging.