It was 3 years before Nube was teaching the students he has right now. At that time, Nube's left hand is still like any other ordinary hand. Until one day, a girl was possessed by an evil spiritual being and Nube volunteered to help the girl.

So, after the school gets over, Nube brought the possessed girl to a class room and started his elimination. He used his crystal making the evil spiritual being that was possessing the girl to appear, unexpecting a tough one. The evil spiritual being that was possessing the girl was an ONI.

One of the toughest phantom. And Nube's power is incomparable with it. But Nube would not give up, gripping tight on to his juzu, his left fist hit against the ONI. Sudden explosion. Nube lost his left hand, his blood was dripping all over. It just looked as if Nube had no chance of winning. But still he didn't surrender to the ONI, as he had promise to his primary teacher, Minako-sensei, who had passed away because of eliminating an evil spiritual being that was possessing Nube.

Nube threw his houten at the ONI but it was no use at all, ONI is just far too powerful for him. The ONI made a powerful blow to him, and Nube is just no opponent for that. Just when about the ONI is gonna kill Nube, there was something that distracted it. The ONI holds its head, looking as if that it's in great pain. Then, a voice, talking to Nube, telling him to seal up the ONI along with "her" now because Nube is her most trusted human being. Nube was confused, he had no idea who was that voice. The ONI's head splited open, within it, it was the face of Minako-sensei, his primary teacher. Nube was shocked, totally confused, and thought that he was dreaming. Minako-sensei tells him that he is not dreaming and he has gotta face this fact. After she died, her soul was forced by evil spirits to the last level of the underworld where we call Hell. The evil spirits that she had eliminated during her lifetime ofcourse would not waste this chance to put a sweet revenge on her. Last, she was absorbed by the ONI in hell. Souls with great spiritual powers are just like a delicious meal. After absorption, she became a part of the ONI. But not knowing if to take it as fortunately or unfortunately, her will and mind remains in the ONI. Just when the ONI is about to bring disaster to the human world, she used her remaining will to make the ONI to go to Nube.

Nube was shocked and confused after hearing what his teacher said. He did not know what to do. While Nube was struggling with himself, Minako-sensei used her power to suppress the power of the ONI so that Nube can seal up the ONI. With tears in his eyes, pain in his heart, Nube run towards the ONI and with a sudden flash of light, the ONI was sealed up on his left hand.

Today, Nube uses his ONINOTE with the ONI seal in it, together with Minako-sensei in it, to eliminate all the evil spiritual being that bothers his innocent students.