The murder episode depicted in this novel is a fiction created by the author Kikuchi; according to the novel, the main character killed his master, a direct retainer of the Tokugawa Shogunate, Saburobei NAKAGAWA, ran away with his master's concubine, became a robber while running a rest house at Torii Pass (Nagano Prefecture), but when he felt his sin, he went into priesthood, started excavation of a tunnel in expiation for his sin, and ended up working together with a son of Saburobei, who followed him seeking revenge, to complete the excavation.
作中では主である旗本中川三郎兵衛を殺害してその妾と出奔、鳥居峠(長野県)で茶屋経営の裏で強盗を働いていたが、己の罪業を感じて出家、主殺しの罪滅ぼしのために青の洞門の開削を始め、後に仇とつけ狙った三郎兵衛の息子と共に鑿ったものとされるが、主殺しなどのエピソードは菊池の創作である。