A plot twist could be that the method Sakura uses to heal Kankuro has an unexpected side effect. For example, it gives him a temporary boost in his puppet - using abilities that he has to quickly learn to control.
One interesting plot twist might be that Sakura's healing of Kankuro is interrupted by a group of rogue ninjas. She has to defend both herself and the still - injured Kankuro. This situation could force her to use her medical skills in creative ways, like using the surrounding plants as makeshift medicine while fending off the attackers.
One idea could be that Sakura uses her medical ninjutsu to heal Kankuro after he gets seriously injured in a battle against a powerful enemy. She has to overcome various challenges like limited supplies and the unique nature of Kankuro's puppet - related injuries.
A possible fanfiction could be set in a post - war scenario. Kankuro and Sakura are part of a group that is trying to rebuild relations between their respective villages. They often have debates on how to best achieve this. Along the way, they also discover that they have more in common than they thought, which leads to a deeper connection between them.
A plot twist could be that Kankuro's past comes back to haunt him. Maybe he had made an enemy long ago and now that enemy targets the reader to get back at Kankuro. This forces Kankuro to face his past and also makes the reader see a more vulnerable side of him. Or perhaps the reader discovers a secret about Kankuro's puppets that changes their perception of him for a while. They have to work through this new information and their feelings for each other.
Another plot twist could be that Madara is being controlled by an even greater force when he captures Sakura. And Sakura realizes this and has to find a way to break the control on Madara while also escaping from him. This would completely change the direction of the story and introduce new challenges and opportunities for Sakura to show her strength and intelligence.
One possible story could be about Kankuro and Sakura teaming up on a mission. In the fanfiction, they start off as just comrades but gradually develop a deeper understanding and friendship. This friendship might then be the base for some interesting character - growth arcs for both of them, like Sakura teaching Kankuro some medical ninjutsu basics in return for him showing her some of his puppet - making secrets.
Maybe there's a plot where Kankuro and Sakura are both chosen to participate in a special ninja tournament. They train together before the tournament, learning from each other's techniques. During the tournament, they support each other and their friendship blossoms as they progress through the various rounds.
One common theme is friendship. Writers often explore how these two characters from different villages can become friends. For example, they might start off as rivals but then find common ground in their love for their respective villages and the shinobi way.
One key element is Sakura's medical abilities. Since she is a skilled medic, she uses her knowledge to treat Neji's injuries. Another element is the relationship building between them. As she heals him, they get closer.
One possible plot twist could be that Sakura initially joins Orochimaru to gain more power to protect her friends, but she soon discovers that Orochimaru has ulterior motives regarding her unique chakra abilities. For example, he might want to use her as a vessel for some dark jutsu. Another twist could be that Orochimaru's henchmen start to develop loyalty towards Sakura instead of him because of her strong will and medical skills. This could lead to a split within Orochimaru's group, with some siding with Sakura and others remaining with Orochimaru.
One idea could be that the child was the result of a past relationship that Sakura kept hidden due to the dangerous nature of the other person. Maybe the father was a powerful enemy who she had to defeat, and she was afraid of the child being used against her.