Noppera-Bou (のっぺら坊 Nopperabō) is the 4th chapter of the Golden Kamuy manga.
Saichi interrogates the captured prisoner and he reveals that he knew nothing about the prisoners being flayed to collect the map. He also reveals that the man who gave them the tattoo called himself Nopperabou because he had no face.
Asirpa begins to paint the tattoo on paper to avoid killing him but the prisoner gets killed by a hooded man with a long-range weapon. The duo creates a distraction and hides until the man who made the shot approaches and disarms him.
Sugimoto starts a fight with the hooded man and when he tries to shoot the man, he easily disarms him. So Saichi comes to the conclusion that the man is a soldier, from the Seventh Division.