Asura Ōtsutsuki

was the youngest son of Hagoromo Ōtsutsuki and heir to his teachings. He is also the ancestor of the Senju clan.

Background
As a child, Asura lived in his genius brother Indra's shadow in every conceivable way, having displayed no natural talent himself. Because of this, Asura came to realise the value of others and their power of the many friends and allies he made before eventually awakening his own power which equalled that of Indra's.

On his deathbed, Hagoromo selected Asura to carry on his dreams of peace for the world. Indra, believing that he should have been chosen, fought Asura to try and claim what he felt should have been his birthright, and they killed each other in this confrontation. Indra's descendants — who would become the Uchiha clan — would continue this fight with Asura's descendants — who would become known as the Senju clan.

Personality
Asura believed that love was the ultimate key to peace, and loved his father greatly as well. Though the son of the famed Sage of the Six Paths, Asura was born with practically no talent, but because of this, he learned the value of depending on and cooperating with others. Through sheer hard work and determination, he was able to awaken his own power. Because he never lost sight of the value in people, he would ultimately become the successor to his father's ninshū as Hagoromo wanted the world to adopt this way of thinking.

Appearance
Asura had short, spiky brown hair — two locks of which were wrapped in bandages framing either side of his face in a similar manner to his brother. He also wore what seemed to be a blank forehead protector. He wore a light-coloured kimono which was adorned with magatama around the collar. The kimono was held closed by a dark-coloured sash. Underneath all of this he wore a black full-body suit.

Abilities
As a child, Asura was considered to be unskilled, much unlike his genius older brother, Indra. Over the years, through gruelling hard work and dedication, plus support from his friends, Asura awakened his own power, his father's "body": life force, stamina, and physical energy; power rivalling that of his brother's. This allowed him to have a greater longevity and strong vitality, as well as massive chakra reserves. He also became a capable leader, obtaining countless loyal followers. It was this way of operating that caused his father to make him the successor to ninshū.

In battle, Asura was seen encased in a three-headed, six-armed avatar wielding several dark-coloured spheres. Although smaller in size, this avatar was capable of going head to head with Indra's final Susanoo. He also seen wielding a shakujō, as well as a sword on different occasions.

Legacy
Hagoromo noted that Asura's chakra remained even after his body was destroyed, and it was reincarnated in various individuals throughout history who all inherited his will. His prior reincarnation being Hashirama Senju. Naruto Uzumaki is the current inheritor of his will.

Asura's ideals also allowed his father to realise a new possibility for the world, and with this he used the Creation of All Things to separate the Ten-Tails' chakra into nine tailed beasts, gave each of them names, in the hopes that when the time came, they would to be reunited as a single entity, yet not as they originally were, and that one shall appear at that time to show them what true power is. The beasts would come to believe this individual to be Naruto centuries later.

According to Black Zetsu, the reincarnations of Indra and Asura are almost always in conflict with each other and rarely work together. Naruto and Sasuke are one of the exceptions, assuming other exceptions have existed throughout the centuries.

Trivia

 * The rivalry of Indra and Asura and their descendants (Uchiha and Senju) is derived from Hindu and Buddhist religions where the Gods, led by Indra, are in constant battle against the Asuras.
 * His battle avatar is befitting of his name, as Asura are often depicted as belligerent beings with three faces and six arms.
 * As Asura believed that love was the key to peace, it is possible that Hashirama Senju's "Will of Fire" evolved from his beliefs. Similarly, his brother's descendants rose to oppose this, inheriting the "Curse of Hatred".
 * Like his father, Asura wielded a shakujō in battle. His choice of weapon could represent his desire for love and peace, while his brother's choice of a sword could symbolise his lust for power.