Yes, there are quite a few. You can start by looking on popular fanfiction websites. Some might focus on their relationship dynamics in the context of the original story's world, exploring how their different personalities interact.
Well, it could be a number of things. Maybe she faces some challenges, has a major life change, or discovers a hidden truth. But without reading the specific novel, it's hard to say for sure.
The cast of the TV series "There's a Tree on Sendai" included Deng Wei, Xiang Hanzhi, Chen Xinhai, and Zhang Weina. Among them, Deng Wei played Su Yishui, Xiang Hanzhi played Mu Qingge/Xue Ranran, Chen Xinhai played Su Yu, and Zhang Weina played Mu Ranwu. These actors would lead the role in this ancient fantasy romance drama.
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.
Another option is Tumblr. There are often fanfic writers who post their works there, and you might be able to find some Himeno x Denji fanfiction by searching relevant tags or following the right blogs.
I haven't read this specific fanfiction, but usually, in fanfictions about Himeno and Hayate kissing in Pretear, it might explore their relationship deeper. It could be a sweet moment of their romantic connection, perhaps a turning point in their story where their feelings are more openly expressed.