In Naruto Chapter 403 Tears, it is revealed that Itachi gave Naruto a gift, a special power to help him in the future. I believe I have discovered the inspiration for that power.
"The Kogarasu Maru or "Little Crow", is a unique Japanese tachi sword rumored to have been created by legendary Japanese smith Amakuni during 8th century CE."
"The Kogarasu Maru is sometimes referred to as a Kogarasu Zukuri as the blade of the Kogarasu Maru was forged in the Kissaki Moro Ha Zukuri design. The Kogarasu Maru is unique as a bridge between the old double-edged Japanese Ken (based on the traditional Chinese straight sword) and the traditional Japanese tachi and eventual katana.
The Kogarasu Maru was designed with a curved double-edged blade approximately 62.8 cm long. One edge of the blade is sharped in normal tachi fashion, but as the edge comes to a point the blade continues in the reverse direction back towards the hilt of the sword, similar to a European sword or a Japanese yari spear, but stopping midway. A single bo-hi style groove runs down both sides of the blade to the hilt. The forging process yielded a sugaha "straight" style temper line on both sides of the blade.
The Kogarasu Maru "Little Crow" is the most famous of the known Kogarasu Zukuri blades and currently in the Japanese Imperial Collection. The tang of the Kogarasu Maru is not signed but the blade is believed to have been made during the either the early Heian period or late Nara period, by the famous Japanese swordsmith Amakuni, who is said to have created the first curved Japanese sword and is believed to have lived during this period. Two other Kogarasu Zukuri blades exist from this era, but many other blades of this type have been created throughout Japanese history."
"There is an ancient legend that attribute this revolution in sword making to Amakuni, traditionally belived to be the maker of Kogarasumaru or ‘Little Crow’, the first curved NipponTo, now in the Imperial Household Collection. According to this legend Amakuni was the Emperor’s swordsmith. One day he saw his lord’s army returning from a battle and the Emperor ignored him instead to give the usual cheers for the good work made with the blades. Then he noticed that many soldiers had broken swords. They where chokuto or straight swords. He was so disappointed of this that he avoid to eat food and drink water for a week, studying a better way to make swords. According to the legend Inari, the Kami of swordsmakers, appeared in a dream to Amakuni, teaching him how to wrap a soft steel core in an harder one, and how a curved edge is more suitable to cuts and more resistant to shocks than the previous straight one. The day after Amakuni made Kogarasu Maru, the ancestor of all NihonTo."
"Ama-kuni of Yamato, who lived about A. D. 700, was a celebrated maker. One of his blades is said to have been carried off by a crow during the reign of Kuwammu-Tenno, A. D. 782, and has since been known by the name of the Kogarasu maru * (little crow). In A. D. 940 Taira Sadamori became the possessor of this sword, which was drawn by him in the wars with Masakado, who was until lately deified at Kanda, Yeddo. "
These are the covers for Naruto Chapter 3 and Chapter 185. We see a "Little Crow" just over Naruto's shoulder. Also, this is the only known chapter cover(at least to my knowledge) that has ever been repeated.
Then there's the cover for Naruto Chapter 11, on this chapter cover we see a crow carrying a sword in it's beak and it appears to be presenting it to Naruto.
Notice in the backgrounds of each cover is the full moon, a clear symbol of Itachi. Naruto Chapter 142 Cover, this is a cover of Itachi with the full moon in the bottom lefthand corner. Naruto chapter 145 page 10 and page 11.
Also, one of the sources Itachi get's his name from is the Kamaitachi. The source of the name kamaitachi is kamaetachi, which means "attacking tachi". It was later changed to the name kamaitachi as a naming pun for "sickle weasel", by Toriyama Sekien. It's also of note that the kamaitachi itself is a wind demon. The Kamaitachi also makes an appearance in the Naruto series as one of Temari's summoning techniques.
Well, there you have it. This is what I believe Itachi gave Naruto. Itachi gave Naruto a legendary sword named the Kogarasu Maru. The sword is most likely a chakra blade, which would allow Naruto to use his wind elemental affinity along with it to cut opponents at a distance.
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