En no Gyōja

was the former leader of the Tsuchigumo clan and the grandfather of Hotaru.

Background
During the Third Great Shinobi World War, he made a peace treaty with Hiruzen Sarutobi. He developed a jutsu capable of destroying an entire village which the Third Hokage proclaims a kinjutsu because of its power. He had two known students in his life. The first was a man named Hāto who was brilliant and exceptionally skilled in ninjutsu, and the second was his granddaughter Hotaru. Feeling that it was his fault the clan fell from glory, En no Gyōja became convinced it was his duty to restore the clan. Before dying, his granddaughter, seeing how much his dream meant to him, begged En no Gyōja to seal the forbidden jutsu in her so she could continue his dream.

Abilities
While the sheer abilities of En no Gyōja remain unknown, and his advanced age presumably hindered his prowess, En no Gyōja was powerful enough to be his clan's leader, and to create a powerful technique that can destroy an entire village. He was also skilled in sealing jutsu, as he devised a way to seal the clan's forbidden jutsu in his granddaughter and safely remove it.

Influence
The name of this character comes from the Japanese ascetic and mystic, the legendary founder of the Japanese religion. The real-life En no Gyōja was born in 634 and is venerated as a mountain saint and a bodhisattva. Many supernatural powers are attributed to him.

In the horror novel Ring by Japanese author Kōji Suzuki, a statue of En no Gyōja gives supernatural powers, including precognition, to the mother of antagonist Sadako Yamamura. Sadako herself is born with the same powers, implying that En no Gyōja is her father. The famous horror film Ring is based on this novel.

Trivia

 * means ascetic. is a surname. when pronounced as eki, it means war campaign or battle; when pronounced as yaku, it means service, role, or use.