UchihaObito
Member
I think when Tobi passes through physical objects he is manipulating his Yang chakra or physical chakra and he cant pass through Naruto when he is in Kyuubi mode because the 4th only sealed the Yin half into him. Tobi effectively creates an inbalance in his and the environments yin and yang chakra that Narutos yin puts back into balance. Thats why he caught a headbutt to the noodle.