Sasukeuzumaki storie

What happens when Naruto and Sasuke are the last ones left and have no where to go after the lost battle? what do they do when the shinigami pulls them into his void and without any help sends them back in time? What do they do when they wake up back in the past? except this time it is different? They didn't wake up in their own bodies, no, they woke up in eachothers