He was not looking at Sasuke's sword, his eyes were facing the enemy.
The sword has no chakra so he could not sense it
The sword is a kusanagi, which means it is stronger than mere metal. Kusanagi can tear through Mokuton easily and go toe to toe with Enma's Diamond stick form. Its sharpness also has a lot of databook hype.
The sword had to cross nearly zero distance to hit Naruto.
How do you block or dodge something you don't know is coming at point blank range?
Naruto's chakra cloak is not impervious to damage. He was burnt by lava before and injured by Juubi's tenpenchi and he admitted that a direct punch from A would be delibitating. He also sprained his ankle when he stomped too hard in punching Kisame.
This cloak should not be compared to a v2 cloak which produces so much chakra that the users skin is burnt off by the sheer amount and the user is in Yamato's words, a mini bijuu. Obviously that would give a greater protection. The markings on Naruto's body are the manifestations of his new seal, not kurama's chakra.
For those saying Naruto is weak and Sasuke is better:
If the blade was in Naruto's hand and Sasuke was the one getting the surprise stab, he would be dying and would need Naruto's yang healing powers to survive.
The sword has no chakra so he could not sense it
The sword is a kusanagi, which means it is stronger than mere metal. Kusanagi can tear through Mokuton easily and go toe to toe with Enma's Diamond stick form. Its sharpness also has a lot of databook hype.
The sword had to cross nearly zero distance to hit Naruto.
How do you block or dodge something you don't know is coming at point blank range?
Naruto's chakra cloak is not impervious to damage. He was burnt by lava before and injured by Juubi's tenpenchi and he admitted that a direct punch from A would be delibitating. He also sprained his ankle when he stomped too hard in punching Kisame.
This cloak should not be compared to a v2 cloak which produces so much chakra that the users skin is burnt off by the sheer amount and the user is in Yamato's words, a mini bijuu. Obviously that would give a greater protection. The markings on Naruto's body are the manifestations of his new seal, not kurama's chakra.
For those saying Naruto is weak and Sasuke is better:
If the blade was in Naruto's hand and Sasuke was the one getting the surprise stab, he would be dying and would need Naruto's yang healing powers to survive.