Prisoner Number One (杉元達を尾行していた囚人, Sugimoto-tachi o Bikō Shite Ita Shūjin) was one of the Abashiri Convicts.
Prisoner Number One has a long face with a pointed nose and black hair which formed a widow's peak with sideburns. He wears a dark vest over a robe tied with an obi as well as white trousers, and leg warmers that reachs up to his calves. He also has his hands wrapped up, leaving his fingers exposed, to keep them warm.
Prisoner Number One is a very cautious man as he could not trust anyone, especially since his fellow prisoners had killed each other for their own desires. He appears to not like direct confrontation as he would sneak around and kill someone from behind. He doesn't seem to hold himself in high consideration either, as he just calls himself a "small time punk" compared to his fellow prisoners.
For unknown reasons, Prisoner Number One was sent to Abashiri Prison. He became acquainted with Noppera-Bou and had a tattoo placed on his body. Sometime later, when the guards were escorting them as a guise to find the Ainu gold, the Abashiri Convicts killed them and turned on each other so that they could claim the gold for themselves. In the midst of this bloodbath, Prisoner Number One ran away, fearing for his life.
In the town of Otaru, when Saichi Sugimoto and Asirpa questioned a brothel owner about a tattoo, Prisoner Number One approached the man, asking him what they had talked to him about. Finding out that they were looking for tattoos, he tailed them as they walked out of the village and into the woods. He wondered just how far they were planning to walk into the forest as he pulled out pistol, preparing to kill them. As he crouched under a fallen tree and came out on the other side, his head got caught in a trap set by Asirpa, which pulled him off the ground, and his clothes got caught in a tree stub, revealing his tattoo.
Prisoner Number One, having been caught by the duo was bounded up and interrogated by Sugimoto asking where the other prisoners are. He reveals that he does not know, as the other prisoners had started killing each other, so he ran away, unable to trust anyone. He became mortified when Sugimoto revealed that the only way to get the tattoo was to skin them all, then told Sugimoto that he'd be better off hunting rabbits. But Sugimoto wouldn't have it, and so Prisoner Number One became tied up in a position where the entirety of his tattoo could be soon. When Asirpa asked him what the man that tattooed him was like, he revealed his name, Noppera-Bou and that he didn't have a face. Before he could elaborate, he was shot in the head by an unknown sniper.
- Prisoner Number One likes soba but dislikes mutton
- His name has never been revealed but Sugimoto calls him "prisoner number one". Shiraishi doesn't recognize his tattoo and calls him a "nobody".