There could be a plot where Sakura is tied up as part of a cultural or ritualistic event in a foreign land she's visiting. This event is misinterpreted by her comrades as a sign of danger. As she's tied up, she tries to communicate with the locals to understand the significance of it all. Meanwhile, her friends are on a mission to 'rescue' her, which could lead to some misunderstandings and humorous or tense moments in the story.
One plot idea could be that Sakura is tied up by an enemy who wants to use her as bait to lure her teammates. Another could be a training exercise gone wrong where she's tied up as part of a difficult survival test. Or perhaps in a more comical scenario, her friends play a prank on her and tie her up, but then things get out of hand when real danger approaches.
One idea could be exploring how she balances her pregnancy with her ninja duties. Maybe she has to take on less dangerous missions but still finds ways to contribute, like training new genin while pregnant.
Perhaps Sakura, being immortal, tries to find a way to end her immortality at some point. She might be tired of seeing her loved ones die while she remains. She could also use her long life to master all forms of ninjutsu, far beyond what any normal ninja could achieve, and then have to deal with ninjas who are jealous or fear her power.
A plot could revolve around the mystery of who the father is. It could add a lot of drama and speculation. Also, Sakura's pregnancy could be a symbol of new hope in the village. She could be seen as starting a new chapter in her life and bringing new life into the world, which could inspire the other characters to strive for a better future.
She might be tied up because she's been captured by an enemy. Enemies could see her as a valuable hostage, either to get information from her or to use her to bargain with her team.
One plot idea could be that Sakura, while on a mission, stumbles upon Pein's base by accident. She tries to use her medical skills to heal some of the injured Akatsuki members there as a way to negotiate peace, which surprises Pein. Another could be a time - travel scenario where Sakura goes back in time and meets a younger Pein before he becomes the leader of the Akatsuki, and she tries to change his path. A third idea is that Pein captures Sakura to use her knowledge of medical ninjutsu for his own purposes, but Sakura gradually makes him see the value of life in a different way.
Maybe Tobirama discovers Sakura's chakra control abilities and decides to study her in order to improve his own understanding of chakra. This leads to a series of experiments and training sessions together, during which they develop a mutual respect for each other's skills and determination.
A more complex plot could be Sakura trying to bridge the gap between the Leaf Village and the Mist Village. As Mizukage, she initiates cultural exchange programs. This includes sharing medical knowledge from the Leaf and learning about the unique water - based ninjutsu of the Mist. Along the way, she faces opposition from traditionalists in both villages but manages to bring about positive change.
One interesting plot could be that Sakura, on a diplomatic mission to Suna, gets lost in the desert and is rescued by Gaara. This encounter leads to a series of exchanges where they both learn about each other's past traumas and how they've overcome them. Another idea is that they team up to fight a new common enemy that threatens both Konoha and Suna, during which they develop a deep respect for each other's skills.
Another plot could be that the tattoo is a mark from a past encounter with an ancient and powerful being. As she tries to uncover the meaning of the tattoo, she gets drawn into a dangerous adventure that involves secrets from the ninja world's history.
One idea could be that Sakura Haruno, as a doctor, discovers a new and rare disease in the ninja world. She has to race against time to find a cure while facing opposition from traditional medical views. Another plot could involve her treating a powerful enemy ninja who holds secrets that could change the balance of power in the shinobi world. And also, she might travel to different villages as a medical ambassador, sharing her advanced medical knowledge and making new friends and allies along the way.