He summons Naruto.. turns out the Naruto who we all know and love actually died in a tragic accident against Zabuza.. as if his stupid shuriken trick would work.
Zabuza instantly realized it was a fake due to Naruto's terrible transformation jutsu.. even Sasuke realized it was fake... As he threw it, Zabuza used a Water Dragon Bullet jutsu to wipe it out, ending Naruto's life.
Little hints were given throughout the series.. his first kiss, Sasuke, abandoning him like he abandoned his team in their time of need... Heartbreaking.
Anyways, he uses the last seven swordsmen (both of them) to put all of their chakra together and summon Naruto (who never really reached of age, and is really still 9)
Kakashi stares in awe and says "No! It cannot be.. A chakra this dark... it is.... it is...!!"
*Silence*..


BELIEVE IT KAKASHI SENSEI ITS ME THE ONE AND ONLY NARUTO AT YOUR SERVICE