There are total characters including DLC characters Boruto and Sarada and Awakenings in the game some characters have more than one. They can be selected individually from the story board. You don't have to finish both fights in a row with an 'S' rank.
Press LT to evade enemy attacks instantly. The best way to get an 'S' rank is to use Chakra Dash and perform a combo. There are two fighting sections that count for this in 'Naruto And Sasuke' and The rest is just cutscenes and the game ending.
However, never get close to her when your substitution bar is empty because you will not be able to evade. If she is coming at you and you do not have enough Chakra to perform a Ninjutsu, you can use Chakra Dash and follow up with a combo costs less chakra and will knock her back. If you have to get into close combat with her, keep pressing LT to evade. Immediately regenerate your chakra after landing a hit and repeat. It is recommended to keep your distance and keep performing the long-range Ninjutsus. After the battle, you can view the score details by pressing X. This Boss battle consists of two chapters.
