Another possibility is a civilian she has known for a long time in Konoha. Perhaps someone who has always admired her from afar, a merchant who supplies the hospital where she works. He might have shown his love and support for her over the years, and finally, Sakura realizes her feelings for him and decides to marry him.
It could be a jealous rival. Maybe there's another ninja who has feelings for Sakura and is trying to keep her away from Sasuke. So Sasuke has to catch her to prevent this rival from taking her away.
Maybe she kisses one of her rivals in a competition. This could be a way to throw the rival off - guard or perhaps it's a moment of sudden understanding between them that leads to the kiss. For instance, if they are in a magical competition and Sakura realizes that the rival has a side to them that she never noticed before, and in a moment of impulse, she kisses them.
Maybe the fanfic could be set in a post - war world. Sakura is tired of the constant fighting and death. She then encounters a kind - hearted artist. He shows her a different side of life, full of beauty and creativity. Their relationship develops slowly. However, Sasuke or Naruto might have some issues with her choice at first. But in the end, she follows her heart and marries the artist. The story could also include how she uses her ninja skills to protect the new peaceful life she has built with her new husband.
Title: 'Sakura's Unexpected Engagement'. In this fanfic, Sakura could be engaged to a mysterious stranger. Maybe he's a powerful wizard from a far - off land. The story could start with Sakura's friends being shocked at the news. They wonder who this person is and what Sakura sees in him. As the story unfolds, Sakura might start to have doubts about the engagement herself, realizing she may have rushed into things without really knowing her fiancé.
Well, it could be a story where Sasuke saves Sakura from someone else who might be a threat. Maybe it's an enemy from another village or a rogue ninja. Sasuke, with his powerful skills, steps in to protect Sakura.
One possible plot could be that Sakura is in an alternate universe where she has lost her memory and kisses someone else thinking they are her true love. Another could be that she is under a spell which makes her kiss someone else, and then she has to deal with the consequences of that action.
First, introduce the fiancé. Is he from a different world? Is he a rival? Then, show Sakura's initial reaction. Is she happy, confused, or forced? Next, add some conflict. Maybe her friends don't approve, or there are some secrets about the fiancé. For example, if he's from an enemy clan. Also, include some internal conflict for Sakura. Does she really love him? Or is she just doing it for some other reason? Finally, build up to a climax where she has to make a decision about the engagement.