Asura Ōtsutsuki

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

Background
Ashura inherited the Sage's "body" — life force and physical energy — and believed that love was the key to peace. When the Sage was on his deathbed, he selected the younger brother to carry on his dreams of peace for the ninja world. The older brother, 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. According to his father, Ashura's personality and background was almost identical to that of Naruto's. Both were born with practically no talent and were able to become as strong as their respective rivals through hard work and dedication. As Ashura matured, he also developed leadership skills and was able to gather countless followers, unlike his brother who stood alone. It was his leadership qualities that ultimate made him the successor to Ninshuu.

Appearance
Ashura has short spiky hair with two locks of hair wrapped in bandages framed 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 inherited his father's incredible life force and physical energy, and also fought using a shakujō which he was presumably skilled at wielding.

When he was a child, Ashura was capable of practically nothing unlike his genius older brother Indra. Over the years, with hard work and dedication, Ashura obtained power equaling that of his brother's as well as the ability to become a leader, obtaining countless loyal followers as well. It was this leadership that chose his father to make him the successor to Ninshuu.

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.