This article contains spoilers from the Naruto series.

Summary

The Rasengan was created by Minato Namikaze to protect Kushina.
The Chidori was a failed attempt to advance the Rasengan.
Kakashi evolved the Chidori into the stronger Raikiri by splitting a lightning bolt.

When it comes to iconic techniques in the Naruto series, it goes without saying that the Rasengan and the Chidori come to mind. Fans know that these two jutsu are not only some of the most powerful to ever exist, but at the same time, are held in a special light by the author and the fans, since they're the signature Jutsu of Naruto and Sasuke respectively.

Minato Complete Rasengan Naruto Rasenshuriken

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By Rei Penber

Just as Naruto Uzumaki learned the Rasengan from Jiraiya, fans know that Sasuke learned the Chidori from Kakashi Hatake. However, few know that the Rasengan and the Chidori are actually linked together. In fact, the Chidori is an actual derivative of the Rasengan, as has been explained by Kishimoto in the Naruto story.

How The Rasengan Was Created By Minato Namikaze

The Rasengan Was Created To Protect Kushina
Minato Observed A Tailed Beast Ball

In the Third Great Ninja War, Minato Namikaze observed a Tailed Beast Ball and then went on to base his own jutsu on it. This Jutsu required him to train with Jiraiya for many years, and eventually, he created what is known as the Rasengan. The original purpose of this Jutsu was to be passed on to Kushina Uzumaki so that she could defend herself in the event that the war resulted in Jinchuriki Warfare and she was sent to the battlefield to fight against the other Jinchuriki. Minato had a first-hand experience of how the other Jinchuriki fought, so he knew Kushina needed something to keep herself safe. Eventually, Minato created the Justu, and Kushina was the one who named it Rasengan.

The Jutsu I'm about to teach you is the legacy of the Fourth Hokage. It's a very special Jutsu. — Jiraiya to Naruto.

Although it is unknown if Kushina learned the Rasengan or not, what fans know for sure is that Jiraiya learned it from Minato, and eventually passed it on to Naruto, the son of Minato and Kushina. The Rasengan became a legacy of his parents which was passed on to Naruto to protect himself, and that's why the technique is as special as it is.

How The Chidori Was Created

The Chidori Is A Failed Attempt At Advancing The Rasengan

When it comes to the Chidori, fans know that it is very different from the Rasengan. Whereas the Rasengan is a powerful Jutsu that creates a spherical ball with high compression and fast rotation, the Chidori is more of a piercing technique that can be used to stab the enemy at a high speed. The creator of the Chidori is yet another genius in the Naruto world, Kakashi Hatake.

I guess it's time to pass the torch. He has surpassed me. — Kakashi on Naruto Uzumaki

Although all fans know this, few know that Kakashi actually created the Chidori based on the Rasengan. The Rasengan was taught to Kakashi my Minato Namikaze, the Fourth Hokage. However, Minato himself was trying to perfect the Rasengan. Although he had limited time, he did what he could, but those around him who knew the technique, such as Kakashi, were trying to complete the Jutsu as well.

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By Rei Penber

Eventually, Kakashi Hatake tried to incorporate nature transformation into the Rasengan, and this resulted in the creation of the Chidori. Kakashi had intended to create the Lighting Release: Rasengan. But what he ended up with was the Chidori. In other words, the Chidori was created by accident and is a failed attempt at perfecting the Rasengan.

The Chidori Evolved Into Raikiri

Kakashi Split A Lightning Bolt With It

Years later, Kakashi Hatake evolved the usage of the Chidori as well and he created a Justu known as Raikiri. Although they're practically the same, the Raikiri is known to be a stronger version of the technique, being S-Rank, compared to Chidori’s A-Rank. How Kakashi improved upon the technique isn't known, but it is said that he eventually made this technique so deadly and fast that he even split a lightning bolt, which is what earned it the name Raikiri, or Lightning Cutter.