Yes, there are likely fanfictions out there with such a plot. The Naruto fandom is vast and diverse, and fans often come up with creative and unexpected storylines. Some fanfictions might explore complex relationships and scenarios where Sasuke has feelings for both Naruto and Sakura in a way that leads to the idea of marriage. However, the quality and nature of these fanfictions can vary greatly.
One scenario could be Naruto finding a rare flower that Sakura has always wanted for her medical research. He goes on a dangerous journey to get it, and when he presents it to her, her face lights up with joy. This shows Naruto's selfless act to make her happy.
The plot could be that Sasuke has been on a long soul - searching journey and has come to the conclusion that his connection with Naruto and Sakura is something he wants to formalize through marriage. He could start by bringing them together and sharing his feelings. Naruto, being the open - hearted person he is, might be more receptive at first, while Sakura could be more hesitant as she has her own insecurities. As they start to explore this new relationship dynamic, they might face opposition from some of the more traditional elements in the ninja world. But through their combined strength and the power of their friendship, they could work towards making this relationship work while also changing the views of those around them.
Another great one is 'Sasuke's Quest for Forgiveness from Naruto and Sakura'. Here, Sasuke is on a mission to earn the forgiveness of Naruto and Sakura for all the pain he has caused them. It's a story full of emotional moments, as Sasuke tries to prove that he has truly changed and wants to be a part of their lives again.
One popular theme is romance. Fans often explore the relationship between Sakura and Naruto in different ways, like what if they got together earlier or how they deal with their feelings for each other. Another theme is adventure. Writers might create new missions for Sakura and Naruto to go on together, with new villains and challenges.
Sakura can be quite emotional in these fanfics. She may cry when thinking about how she let Naruto go or when she faces difficulties in getting him back. But she also uses these emotions to fuel her determination. She'll often pour her heart out to Naruto when she finally gets the chance to talk to him.
He also defends Sakura's honor. If someone in the village were to say something unkind about her or her work, Naruto would quickly step in and set them straight. This protects Sakura from negative emotions and helps keep her happy. Moreover, Naruto often shares his own experiences and lessons he's learned to inspire Sakura. He tells her about how he overcame difficulties in his training, which gives her the motivation to keep going in her own pursuits and be happy with her progress.
A great fanfiction in this category is the one where Sakura discovers a hidden prophecy about Naruto's disappearance. She then devotes herself to understanding the prophecy and using it to her advantage to get Naruto back. This fanfiction delves deep into the Naruto universe's lore and Sakura's character development. It also has some really interesting plot twists as Sakura uncovers secrets about the village and Naruto's true nature while on her mission to bring him back.
You can try Archive of Our Own (AO3). It has a vast collection of Naruto fanfictions. Just search for tags related to Sasuke, Naruto, and Sakura. There are likely many stories that explore Sasuke's desires regarding Naruto and Sakura there.