Obviously Naruto would be one of the main characters. Since it's about him flashing to the future, he is the central figure through which the story unfolds. Sasuke could also be a main character. Maybe in the future, he has his own new goals or challenges that Naruto has to either help with or oppose. Sakura might also play an important role. She could be a powerful medic - ninja in the future and be crucial in treating the injured during some sort of conflict.
In this 'flash to the future naruto fanfiction', Naruto is the key, but Hinata could be a major character too. In the future, she might be leading the Hyuga clan in a new direction. Shikamaru, with his high intelligence, would likely be involved in any sort of strategic planning in the future. He could be an advisor to Naruto or have his own independent plans to deal with the new situations in the future. And of course, Kakashi could still be around in some form, perhaps as an elder statesman guiding the younger generation.
Main characters would surely include Naruto as he is the one traveling to the future. Boruto might also be a main character. He could be in a position of great power or responsibility in the future. Mitsuki, being an artificial human, could have some unique role in the future world. Maybe he has developed some new abilities that are crucial to the future of the ninja world. Additionally, Sarada could be important. She might be on a journey to prove herself as a worthy successor to the Uchiha name in this future setting.
If you want the clearest chapter reference, go to Chapter 184. Early on, Jiang Li can finish the competition alone???; later, the chapter leans on Then isn't the championship undoubtedly hers?.
If you want the clearest chapter reference, go to Chapter 159. Early on, Seeing the red light of the camera turn on, Su Yinwan looked at the...; later, the chapter leans on Sorry, director, it was my staff who didn't arrange things well, that's....
A practical answer is Chapter 186, because it turns the idea into a concrete scene. The chapter opens with Seeing Wen Jiaojiao bravely entering the pigsty, Jiang Yan couldn't stay..., adds pressure through Thinking this, he subconsciously looked towards the front of the crowd..., and ends on And.
If you want the clearest chapter reference, go to Chapter 139. Early on, Wen Jiaojiao's live stream was inundated with a wave of question marks.; later, the chapter leans on Princess Wen, what are you doing?.
The best chapter pointer here is Chapter 174, "Such a Melodrama, Love Watching It". It opens with Does Young Master Jiang really care why I would come here? and closes on She knows the camera is on her, how can she still..." Jiang Li glanced at....
A practical answer is Chapter 134, because it turns the idea into a concrete scene. The chapter opens with After a brief noon rest, the production team was up to their antics again., adds pressure through Thus, Jiang Li's live stream was once again flooded with netizens coming..., and ends on [Are.
If you want the clearest chapter reference, go to Chapter 172. Early on, Not only Shu Yan, but the entire internet was shocked when they saw Su...; later, the chapter leans on Damn, what brand of make-up is Su Yinwan using?.
Look to Chapter 137 for the clearest answer. It begins with Jiang Li personally went to Lai Fu's tomb and performed a small ritual., keeps building through After it was finished, she took out talisman paper and gently waved it..., and lands on At that moment, Qi Tianyu had just finished his.
The best chapter pointer here is Chapter 159, "The Other Flying Guest is Actually Him?!". It opens with Seeing the red light of the camera turn on, Su Yinwan looked at the... and closes on Shang Shaobai, who was browsing through files, received a call from his....
A practical answer is Chapter 168, because it turns the idea into a concrete scene. The chapter opens with Su Yinwan spoke those words with a pitiable expression, then lowered her..., adds pressure through But this time, for lunch, Jiang Li cannot help, the rest of you must..., and ends on The Gu.