A mysterious ayakashi that was sealed in a shrine until he was accidentally released by Natsume Takashi. Since Madara was trapped in a material form for so long, he ordinarily takes on the shape of a maneki neko (lucky cat), leading Natsume to nickname him Nyanko-sensei. In this form, other people can see him.
He is a powerful ayakashi, who protects Natsume from others and teaches him spells on occasion, in return for Natsume's promise to give him the Book of Friends when he dies. As the story progresses, Madara takes a liking to Takashi.

Source:Wikipedia

Unlike his siblings and father, he does not wear a tokin. He had his mohawk hairstyle since birth and Karasu Tengu also mentioned that Tosakamaru is as "wild as an eagle".

Source:Wikipedia JP

Nurarihyon is Rikuo's grandfather, known as the master of all spirits or as the Supreme Commander. It is said that he plays pranks and hates humans, but he doesn't really hate them - rather, he doesn't believe humans should interfere in yōkai affairs. He dislikes the fact that Rikuo goes to school and acts human but respects his wishes.

400 years ago, he fell in love with Yōhime and fought with the Hagoromo-Gitsune in Kyoto for Hagoromo-Gitsune kidnapped Yōhime to eat her liver.. At first things looked grim for Nurarihyon, but when Hagoromo-Gitsune mocked him, Nurarihyon finally was able to slash Hagoromo-Gitsune's current body host, saving Yōhime. But Hagoromo survived the slash and fled to the roof where Nurarihyon followed her. They then clashed again for the second time, this time on the roof with both being equally matched. It was only when Keikain Hidemoto arrived and tip the balance of scales in favor of Nurarihyon by helping Nurarihyon battle Hagoromo-Gitsune. Both defeated Hagoromo-Gitsune but before the host Hagoromo-Gitsune was residing in, she was able to puncture through Nurarihyon and took his heart and consumed it to restore a bit of her strength which left a gaping hole in Nurarihyon's chest and caused Nurarihyon's life span to decrease. When Nurarihyon was In his prime, he and Keikain Hidemoto were considered friends. Even in his old age, he can easily best "Night" Rikuo and Muchi. Normal demons feel so much "Fear" that he is invisible to them until he strikes, that is his "Meikyō Shisui".

He is still able to appear in his younger-form, as shown in an episode in "Demon Capital", despite usually appearing in his older and usual self, as Rikuo's grandfather.

Nurarihyon is Rikuo's grandfather, known as the master of all spirits or as the Supreme Commander. It is said that he plays pranks and hates humans, but he doesn't really hate them - rather, he doesn't believe humans should interfere in yōkai affairs. He dislikes the fact that Rikuo goes to school and acts human but respects his wishes.
400 years ago, he fell in love with Yōhime and fought with the Hagoromo-Gitsune in Kyoto for Hagoromo-Gitsune kidnapped Yōhime to eat her liver.. At first things looked grim for Nurarihyon, but when Hagoromo-Gitsune mocked him, Nurarihyon finally was able to slash Hagoromo-Gitsune's current body host, saving Yōhime. But Hagoromo survived the slash and fled to the roof where Nurarihyon followed her. They then clashed again for the second time, this time on the roof with both being equally matched. It was only when Keikain Hidemoto arrived and tip the balance of scales in favor of Nurarihyon by helping Nurarihyon battle Hagoromo-Gitsune. Both defeated Hagoromo-Gitsune but before the host Hagoromo-Gitsune was residing in, she was able to puncture through Nurarihyon and took his heart and consumed it to restore a bit of her strength which left a gaping hole in Nurarihyon's chest and caused Nurarihyon's life span to decrease. When Nurarihyon was In his prime, he and Keikain Hidemoto were considered friends. Even in his old age, he can easily best "Night" Rikuo and Muchi. Normal demons feel so much "Fear" that he is invisible to them until he strikes, that is his "Meikyō Shisui".

He is still able to appear in this form, as shown in an episode from "Demon Capital", despite his old age/normal appearance that he usually appears in as Rikuo's grandfather.

Info:
Introduced in the first half of the manga, Jiraiya appears as a perverted old man whom the lead character, Naruto Uzumaki, refers to as "Ero-Sennin" (エロ仙人 or "perverted sage"). It is established that he was a student of the Hidden Leaf Village's Third Hokage, and one of the Three Legendary Sannin shinobi, along with Orochimaru and Lady Tsunade.

Abilities:
Jiraiya is known as the "Toad Sage" (蝦蟇仙人). Having been trained by toads to utilize their secret arts, Jiraiya can summon them to his side as allies during battle and if need be, he can also summon parts of toads, e.g. blanketing an area with a toad's esophagus to immobilize and trap an opponent.
In the second half of the series, Jiraiya is shown to possess a number of toad-based abilities not wholly reliant on summoning. Most prominent of these is being able to enter the "Sage Mode" (仙人モード), a transformation that drastically increases his physical abilities and the strength of his attacks.

Source:WIkipedia

Info:
Orochimaru was created as one of the series' main antagonists.
In the anime and manga, he is a former ninja of the village of Konohagakure and a former disciple of the Third Hokage. As he grew older Orochimaru, along with Jiraiya and Tsunade, collectively became known as the "Legendary Three Ninja" or "Sannin" (伝説の三忍), due to their exemplary ninja abilities.

Much of Orochimaru's arsenal of abilities deals with snakes.
During his time in Konohagakure, Orochimaru distinguished himself as one of the village's most powerful ninja; however, his desire for power led him to obtain a means for immortality by transferring between different host bodies. This desire for a host is one of his driving motivations throughout the series, resulting in his desire to acquire Sasuke Uchiha due to his powerful genetic heritage.

Source:Wikipedia