One possible plotline could be that Naruto leaves with Tsunade on a mission to find a rare herb that is said to have the power to heal any wound. Along the way, they face various enemies who also want the herb for their own malicious purposes. Naruto's skills and Tsunade's wisdom would be put to the test as they battle their way through.
Another plot could be that Tsunade decides to take Naruto on a journey to meet some of the most powerful ninjas in other villages for training. Naruto is excited to learn new techniques. On their travels, they encounter different cultures and ninjutsu styles. Tsunade acts as a guide and mentor, and Naruto has to adapt quickly to the new challenges presented by these foreign ninjas.
One possible plotline could be that Naruto discovers a new form of chakra control that gives him an edge over Tsunade. He uses this to take charge in a dangerous mission where Tsunade was initially leading.
Well, if there is such a fanfiction, perhaps there's a plot where some sort of magic or jutsu affects their minds. Naruto might be under a spell that makes him see Tsunade in a romantic way, and Tsunade, being affected by a similar or related jutsu, reciprocates. And so, in this strange situation, they end up in a situation where they'sleep together'. But this is all just speculation based on what could be in a very unorthodox fanfiction.
Another plotline might be that Tsunade is affected by some kind of dark magic or genjutsu that makes her turn against Naruto. Naruto, realizing it's not really Tsunade's fault, still has to fight her to try and break the spell. He could call upon his friends for help, but in the end, it's his determination and his bond with Tsunade that helps him reach her and break the control.
One possible plotline could be that Tsunade and Naruto go on a dangerous mission together and Tsunade has to protect Naruto at first, but then Naruto's growth allows him to contribute significantly. Another could be that Tsunade is teaching Naruto some special medical jutsu, and they have a mentor - mentee relationship throughout the story.
A possible plotline could be a training arc. Tsunade could be training both Naruto and Sakura in a new and advanced form of combat or medical ninjutsu. This would involve a lot of character development as they struggle to master the new skills. For example, Naruto might have trouble with the precision required in a medical - related technique while Sakura helps him out, and Tsunade observes and gives tough love guidance.
One possible plotline could be that Naruto discovers some long - lost secret about his mother Kushina and decides to leave the village with her to explore this mystery further. Maybe they are on a quest to find some hidden power or knowledge that is related to Kushina's Uzumaki heritage.
One possible plotline could be that Naruto accidentally travels back in time and lands right in front of Tsunade when she was at a crucial point in her life, like just after the death of her loved ones. Naruto, with his future knowledge, helps her cope and in the process, they grow closer. Another plotline could be that Tsunade is sent to the future where she meets an older and more mature Naruto. They initially clash due to their different outlooks from different times but then gradually fall in love as they understand each other better.
One plotline could be about Hinata and Tsunade helping Naruto in his diplomatic missions. Hinata with her gentle nature could be good at building relationships with other villages, and Tsunade with her experience and leadership could guide Naruto in making tough decisions.
A possible plotline could be about family secrets. Tsunade might reveal some long - hidden family secrets to Naruto that change his perspective on his family and his place in the village. For example, she could tell him about a special kekkei genkai that runs in the family that he might inherit.
One possible plotline could be that Naruto is somehow tricked into leaving with Kisami and Itachi. Maybe they convince him that there is a greater threat that only they can help him face. Along the way, Naruto might start to learn more about their motives and the secrets of their pasts. He could also be in a position where he has to use his own skills and values to influence them.