Asura Ōtsutsuki

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

Background
As a child, Ashura lived in his brother's shadow in every conceivable way, having no natural talent. While constantly struggling to improve himself, Ashura matured emotionally as he made many friends and allies, eventually making his own talents blossom and finally catching up to Indra. When the Sage was on his deathbed, he selected the younger brother to carry on his dreams of peace for the ninja world. His older brother Indra, believing he should have been chosen, fought him to try and claim what he felt he deserved. The descendants of the elder brother, who would become the Uchiha clan, would continue this fight with the younger brother's descendants, who would become the Senju clan.

Personality
Ashura believed that love was the ultimate key to peace, and loved his father greatly as well. Though the son of the famed Sage, Ashura born with practically no talent but because of this, he, unlike his brother learned the value of depending and cooperating with others. Though sheer hard work and determination, he was able to awaken his own power. Because he never lost sight o 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
Ashura had short spiky hair with two locks of hair 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 markings on the sides but no symbol on the metal piece.

Abilities
While virtually nothing is known of his abilities, Ashura fought using a shakujō which he was presumably skilled at wielding.

When he was a child, Ashura was considered to be unskilled much unlike his genius older brother Indra. Over the years, with hard work and dedication, Ashura obtained power equal to that of his brother's and awakening his inherited life force and physical energy of his father. He also become a capable leader, obtaining countless loyal followers as well. It was this leadership that chose his father to make him the successor to Ninshuu. In battle, Ashura was seen encased in a two-headed, six-armed avatar wielding several black balls.

Legacy
According to Hagoromo, after Ashura's body was destroyed in a war, his chakra remained, and Ashura was reincarnated in Naruto Uzumaki.

Trivia

 * As the younger brother was born with the "willpower" of the Sage of the Six Paths and desired peace, it may be possible that Hashirama Senju's "Will of Fire" refers to this. Similarly his brother's descendants rose to oppose this, inheriting the "Curse of Hatred".
 * Like his father, Ashura 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.