Onigumo typically tries to present himself as a quirky cheerful person with a smile on his face, but the cool detachment of his gaze and his calculating eyes often make any attempts on his part to appear harmless ring false. Onigumo is, by nature, a scientist first and a teacher second. Viewing his students past and present as test subjects for his experiments and further data-points in regards to his theory. The theory in question being the application of the simple belief of "Survival of the Fittest" in regards to what makes a truly powerful Shinobi. Onigumo himself tends to appear at all times calm, patronizingly so, in a detached and scientific manner. He rarely gets attached to his students and tends to take a twisted sort of pride in those he views as having been held to his fire that have come away stronger for it. He prefers to be in control at all times and enjoys the power his position lends him in regards to shaping the fates of others.
Tall and slim with pale white hair that has almost a pastel violet tinge to it, pale skin, and eyes as black as charcoal everything about Onigumo appears stark, clean, and utterly unruffled. His control absolute in regards to not only his surroundings, but himself. His tendency to prefer black and white yukata's and haori's only adds to his monotone appearance with his false smile lending his otherwise possibly handsome face a false and mask like appearance not unlike that of a Kabuki player.
Born to the Yoi clan Onigumo chose to emulate the scientist caste of the clan proving exceedingly intelligent and observant and graduating the academy with high marks. Thus meeting all expectations his clan held for him. He spent a good deal of time studying under Dai Ri and was briefly considered by the Warden for the position of apprentice and his successor. Onigumo however, proved to have far too much of a taste for control and the power that came along with it and was instead passed over by the Warden. Leading the Yoi to seek a position outside the Prison where he would have ample test-subjects upon which to experiment. His experiments in regards to the "Survival of the Fittest" and his theories in regards to what conditions environmental or genetically lead to producing the most superior of Shinobi intrigued the Yoi who acquired for him a position in Yukigakure's academy to put his hypothesis to the test.
Yoi Onigumo began his position at the academy in -4ASD taking over a class two years from graduation when their previous Sensei had seen fit to suddenly retire due to the Yoi's encouragement. The class itself was an advanced placement class for those students on the potential Jounin fast track and was a perfect mix of clan children, second and third generation Shinobi offspring, and even surprisingly a few civilianborns. A perfect first sample size and test bed for Onigumo to prove his theories worth to his clan. The new Academy Sensei would spend his first year with his students getting to know them, earning their trust, taking detailed observations of their abilities, mental state, and backgrounds as he formulated theories of how each might deal with potential life threatening opposition. In the end once his assessments were complete come the following year Onigumo set his plan into motion. Looking back upon his first test Onigumo would admit it had far too many variables in his excitement to have viable subjects to study and that had things gone a little differently he might not have had any living test subjects to observe. Yet while some of his students remained suspicious and wary of them, all trusted his authority as their Sensei enough to follow the Yoi out of the village and onto the tundra for a survival exercise. Pairing his students into groups of seven to work together Onigumo carefully ensure his best mix of students in terms of varying skills, backgrounds, and genetics, were placed together in the group farthest from the main cluster. When the blizzard the farthest ships of the Yukigakure fleet had picked up and notified the Yoi about finally made land Onigumo ensured said group was not among his students collected in his 'haste' in the near white out conditions and ushered to the safety of a nearby outpost. Leaving the scientist to wait to collect his results.
The incident was ruled a tragedy as one of the worst blizzards in Yuki no Kuni's history swept across the land raging for two weeks. When the storm had finally passed and his students still failed to be recovered Onigumo began to grow concerned that there might be no living subjects to collect. It would be three weeks since the loss of his students before a patrol would report encountering a group of half-feral pre-genin matching their descriptions. When Onigumo would bring it upon himself to visit them in the hospital as any concerned Sensei should he would find that of the seven students he had left only three had returned. One of which the ringleader, a civilianborn shinobi bastard of a girl by the name of Akaishi Katsumi, took it upon herself to try to kill him. Her attempt failed as she was too weak from her ordeal to fight off the doctors that restrained her having used the last of her strength to lunge for his throat with her teeth, but her viciousness would be carefully noted. Though the girl would later on apologize for the attempt blaming it on sickness and hallucinations with a smile that held even less warmth then his own it was clear she as only apologizing in truth for failing to finish the job. She would go on to watch Onigumo for the remainder of the year with the same sharp, intelligent and feral eyes with which he observed her much to his pleasure. She would never again trust him, but her existence as an anomaly in his date, and her continued survival beyond the academy despite all odds would lend his theory credit and cement his position as an Academy teacher and among the Yoi.
Onigumo himself has now been teaching successfully at the Academy for eight years. While his record is pocketmarked with unfortunate accidents and incidents befalling his students, none quite so serious as his first experiment, they have thus far been unable to be traced back to the man himself. All, at least to the public, appear to simply be unfortunate misfortunes of fate rather then the careful planning of a scientific mastermind.
Akaishi Katsumi: An anomaly in Onigumo's data, his first test subject, and most resilient student. Katsumi is thus far the crowning achievement of his experiments and the greatest embodiment of his theories.