Tamamo, also known as Kyousuke Tamamo in his human form, is the most important of the youko in the manga series, a powerful being who is both Nube's ally, and ultimate rival.

First arriving at Doumori Elementary as a bishonenous male teacher who wins the hearts and minds of his students and fellow staff, his true intent was to seize the skull of Nube's student Hiroshi Tateno which is his "perfect skull" for transforming into a human. When Nube was forced to come to Hiroshi's rescue, the two got into an intense battle upon which the true form of the golden fox-creature was revealed and nearly defeated Nube. Due to Hiroshi's courage, however, Tamamo was defeated, though not for good. He returned soon after, intrigued by Nube and how his powers was amplified when fighting for his students. He learns that it is the power of the human heart, and not understanding it, tries to know more by creating situations that force Nube to fight or via simple observation. Tamamo also abandoned his teacher's disguise to work as a doctor in Doumori Hospital, where his 400 years of knowledge accumulated to cause misery went into healing others, which he thought would be a good way to learn more about humanity.

Having existed and trained his spiritual powers for centuries, Tamamo has become adept in many spiritual powers and abilities that he holds even without perfecting his "transformation jutsu." He is a master of "illusion jutsu," able to manipulate anyone to see whatever he portrays as long as there is motion. (even to the extent of creating clones of himself off the display of video game screens) Offensively, he uses a "youko foxfire jutsu," allowing him to create and control a powerful fire-based attack which he can increase and power and intensity to burn his opponents. He can also handle certain other spiritual abilities like Nube's such as assisting in controlling spiritual energy and even the "youshin jutsu." When not using spiritual power, his main weapon is a paw-like neck catcher, which primary function is the extraction of suitable skulls for his "transformation jutsu," but can also be broken apart to surround himself and an opponent within a barrier for more powerful attacks. In the manga, it was revealed that the skull he was currently using in the course of the series came from a dead mountain climber, who was a well-to-do college student. The encounter between Tamamo and the student's fiancee marked one of the important turning points in his character development.

At the start of the series, Tamamo merely seems like a powerful youkai who manipulates and fights as a means for his own selfish desires. After fighting alongside Nube and class 5-3 and solving a number of youkai problems, he grew fonder and fonder of the human race, to the extent that he would use "Megido," his most powerful fire-based ability, in order to destroy Zekki, the younger brother of Nube's Oni no Te. Tamamo also found himself unable to take Hiroshi's skull even when the opportunity presented himself later on, having learned too much of the human heart. This is a problem for him, as without a suitable skull his mental and physical faculties would eventually erode, leaving him to die as only a shell of his former self.

In the manga liner notes for Volume 2, the author stated that Tamamo was intended to be a direct descendant of the Nine-Tailed Kitsune who was notorious as Tamamo no Mae. However, the fox appeared later in the story and was less than fond of Tamamo, thus leaving the name to be most likely an allusion, perhaps out of respect.
(Source: Wikipedia)