One possible plot detail could be that they start off by reminiscing about their old adventures during the walk. Naruto might crack some of his usual jokes to make Sakura laugh. They could also talk about their friends and how everyone has changed over time.
The walk could be a time for Naruto to finally confess his deeper feelings for Sakura. Maybe he has been holding back for a long time, and as they stroll through the familiar paths to her home, he gathers the courage to be more open about his emotions. Sakura, on the other hand, could be initially shocked but then start to see Naruto in a new light.
In this fanfiction, perhaps Sakura is kidnapped by a group who wants to use her medical skills for their evil purposes. Naruto quickly sets out to rescue her. He uses his newfound powers and the help of his friends like Kakashi and Shikamaru. When he finds Sakura, she is weak but still defiant. Naruto has to fight the kidnappers, and his determination to bring Sakura back home gives him the extra strength he needs to defeat them all.
It could be Orochimaru. He might be interested in Sakura's potential as a medic - ninja and wants to use her for his experiments. Naruto would then have to face Orochimaru once again to rescue Sakura and bring her home.
Well, perhaps in this fanfiction, Naruto is put in a situation where he has to hypnotize Sakura to protect her from an enemy. The enemy is after some information that only Sakura knows. Naruto hypnotizes her to make her forget the information temporarily so that the enemy can't get it. This could lead to a series of events where Naruto has to keep Sakura in a hypnotized state while they figure out how to deal with the enemy.
Their conversation could also be more personal. Naruto might ask Sakura about her family, and Sakura could share some heartwarming stories. She might also ask Naruto about his time away from the village on his long missions. And Naruto would tell her all the interesting things he saw and the people he met. There could be some light - hearted banter in between, like Naruto teasing Sakura about her temper.
In the fanfic, Sakura might be influenced by some dark force or a bad character. She starts to act against Naruto and their friends. Naruto, being the hero, tries to reason with her first but when she attacks him, he punches her back. This punch snaps her out of the influence, and they join forces again to fight the real enemy.
Perhaps there was some sort of dark influence at play. In the world of Naruto, there are often dark forces and genjutsu (illusion techniques). It's possible that Naruto was under the influence of a genjutsu that made him see Sakura as a threat, so he punched her in self - defense without realizing it was an illusion.
The plot could involve Sakura getting a chance to relive parts of their past. She might try to save Sasuke's family, which could change Sasuke's entire motivation and path. This would have a huge impact on the Naruto universe as we know it.
It could be about Naruto coming back to the Hidden Leaf Village after a long and mysterious journey. Maybe he has new powers or knowledge that he uses to protect the village from a new threat.
One possible plot could be that Naruto finally asks Sakura out on a date after years of pining. They could start the date at Ichiraku Ramen, reminiscing about old times. Then they might take a walk in the park, where Naruto shows Sakura a new jutsu he's been working on. Sakura is impressed and they end the date with a sweet kiss on the cheek as the sun sets.
One possible plot could be that Sakura uses a new jutsu she's been working on accidentally and it turns Naruto into a girl. Naruto then has to deal with the sudden change, like how people in the village react differently to him/her. Maybe he/she has to learn new ways of fighting as a girl, with different physical abilities. And there could be some comical moments as Naruto tries to adapt to wearing girl's clothes and doing girl - like things.