Book 1chapter 1:

we see a planet that looks close to destruction as we zoom into the Leaf Village. We see three people surrounding a scroll. As one says well guys this is the final chance to save the world from Total annihilation. That's right now let's focus on the teleportation scroll. See in the far distance three figures as they get closer you can tell they are oatsuzuki momoshiki, kenshiki, urashiki. As boruto, naruto, and Sasuke see them they start to quickly put chakra into the teleportation scroll starts to glow there was a bright light that forced there eye's closed. Upon opening their eyes see a world filled with Greenery and beautiful Skies but along with teleporting to another world the chakra build up to send them there kill them due to the immense chakra drain to send them to a new world. Due to the large chakra trees were created throughout the world to purify the chakra so life could continue to grow.