This story is also told all over Japan in various forms. In some cases, the wolf is replaced by she-demon (Niigata) or a shape-shifting cat. The wolf version below is largely translated from a collection of folklore entitled, 日本の民話（四国編）(Japanese Folklore – Shikoku) compiled by Marihiko Fujiwara (藤澤衞彦) and can be purchased in Japanese from various sellers online relatively cheaply (about $3.00). I tried to remove any embellishments obviously added by an editor that got in the way of the story.
The version below is true to the repeating elements in most of the versions I could find.
Long ago, a samurai was traveling through a winding mountain pass.
He had intended to stop somewhere for shelter for the night, but the sun set faster than he had expected. From the distance, the sound of wolves howling reached his ears. It was an eerie and terrifying sound. The samurai saw a large tree a little off the path and hurried over to it. He climbed to a suitably high branch to spend the night.
It was particularly dark in the tree as the branches obscured his view of the stars and moon. He could hear the howls of the wolves coming closer and closer.
When he could hear that the breathless wolves were about to pass by, he crouched down to hide himself. But perhaps the wolves could smell him because they came to the tree and howled. In the distance he could see many eyes reflecting blue light in the dark coming towards him. The wolves surrounded the tree howling in hunger and anticipation.
It was too dark to be sure, but counting eye reflections, the samurai tallied over 300 wolves. Among them, one let out an eerie high-pitched howl as if it was a signal and charged towards the tree. It was a terrifying sound, and as though it had some strange power over the others, the other wolves rushed towards the tree attempting to leap onto its lower branches. But they all failed and the samurai sighed in relief.
However, suddenly one wolf managed to make the leap onto the lowest branch and one by one the others followed suit. The samurai drew his sword and began hacking at the wolves. But it seemed as soon as he cut one down, another was in its place nipping at his arms. The samurai swung his sword fiercely and managed to cut one of the wolves in half. As he did so, it let out a death cry as it fell. The samurai went into a frenzy swinging his sword up and down and left and right.
Seeing this, the wolves fell back for a moment in hesitation and the samurai, his eyes now adjusted to the dark, took the chance to crane his neck and look below. To his astonishment, he saw hundreds of wolves making a ladder with their bodies. The samurai readied himself for more fighting.
He heard strange sounds like human conversation from the wolves below.
As soon as the sounds had ended, three wolves came running at the samurai, but he dispatched them expertly. From below, more wolves ran up the living ladder and continued to attack relentlessly. As soon as he cut one down, another appeared. As if driven by some evil force, the wolves clambered over the dead bodies of their fallen members, pushing and shoving each other to reach the samurai.
After a long fight, finally the wolves pulled back and stopped attacking.
Human speech could be heard coming from the wolves below.
“Call the blacksmith’s mother.”
“She can help us.’
“Yes, call her.”
The group fell apart and three wolves ran off into the distance. After a while, the samurai heard a dreadful howl and a new living ladder was made. A wolf leapt straight to the top of the ladder. It had some kind of pot covering its head like a helmet.
“You monster!” shouted the samurai. He ran at it and struck the helmet with the handle of his katana with all his might.
“Aaaagh!” cried the wolf as it fell down to the ground. The remaining wolves scattered in fear.
Shortly thereafter, the sun rose and the samurai came down from the tree. He saw the wolves’ dead bodies piled on the ground.
From the pile of dead bodies, the samurai could see a trail of blood drops. He followed the blood drops until he came to a blacksmith’s house. He entered and heard someone say reproachfully, “Who is it?”
He replied, “And who are you?”
“I am the blacksmith but there is a sick person here today, and I would like to keep everything quiet.”
“Who is sick? I will see them. I am carrying medicine with me,” said the samurai.
“That would be wonderful! Last night my mother went to the river to wash a pot, but she hit her head and is injured. It’s good timing that you came today. Please go look at her.”
The blacksmith led the samurai to the back of his home.
When the blacksmith’s mother saw the samurai, she suddenly howled. She transformed into her true shape and ran at the samurai. The samurai did not hesitate. He swung his sword and struck a fatal blow to the wolf that had transformed into the blacksmith’s mother.
The blacksmith was in shock. “A wolf monster! But where is my mother?”
The dying wolf’s eyes turned to the floorboards as it breathed its final breaths. When the samurai and blacksmith looked under the floorboards they discovered the true mother’s bones.