Asura Ōtsutsuki

was the youngest son and heir of Hagoromo Ōtsutsuki as well as the ancestor of the Senju clan.

Background
As a child, Asura lived in his genius brother's shadow in every conceivable way, having no natural talent himself. While constantly struggling to improve himself, Asura matured emotionally as he made many friends and allies, eventually making his own talents blossom and finally catching up to his older brother, Indra. On his deathbed, Hagoromo selected Asura to carry on his dreams of peace for the ninja world. Indra, believing that he should have been chosen, fought Asura to try and claim what he felt he deserved. His descendants, who would become the Uchiha clan, would continue this fight with Asura's descendants, who would become 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 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 forehead protector with no symbol on the metal piece. 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 hard work and dedication, plus support from his friends, Asura awakened the inherited power of his father's body, life force, and physical energy and ultimately obtained power equal to that of his brother. He also had become a capable leader, obtaining countless loyal followers. It was this leadership 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. This avatar was capable of going head of head with Indra's final Susanoo. He also wielded a shakujō as well as a sword on different occasions.

Legacy
According to Hagoromo, Asura's chakra remained even after his body was destroyed, and it was reincarnated though various individuals throughout history which inherited his will. The second-to-most recent reincarnation being Hashirama Senju. Shortly after Madara's death and the transmigration ready to begin once again, Asura was reincarnated into Naruto Uzumaki.

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 the nine tailed beasts, give them each 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.

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.