Description of the oneshot Kikai Tonchibanashi - Hanasaka Ikkyuu:

One-shot published in Akamaru Jump.

Long ago, there was an ayakashi who challenged his victims to a battle of wits. If the subject succeeded, the ayakashi would grant them one wish, but if they lost, he would devour their soul. Only one person has been able to consistently defeat this ayakashi and his tricks: the clever Hanasaka Ikkyuu. The ayakashi follows him, ever eager to eat his soul, but for Ikkyuu, using the ayakashi's power to help others is worth the risk! When he chances upon a Yukionna (snow fairy) desperately in need of his ayakashi-extracted help, will his cleverness finally run out?

Description of the oneshot Kikai Tonchi Banashi Hanasaka Ikkyuu

One-shot published in Weekly Shounen Jump.

Long, long ago, there lived an eccentric spirit. One who ate the souls of humans and loved "riddles". He would ask anyone who crossed his path sadistic "questions", and if they returned a "stupid answer", they would have their souls eaten without a moment's delay. On the other hand, if they answered with "wit", the spirit would grant a single wish, regardless of what it was. There was a bald, witty genius of a boy who responded magnificently to the spirit's "question". His wish was for the spirit to possess him for the rest of his life!

Description of the serialization Kikai Banashi Hanasaka Ikkyuu:

There once was an ayakashi called Karma who challenged his victims to a battle of wits. If the subject succeeded, the ayakashi would grant them one wish, but if they lost, he would devour their soul. At the same time, there was a young monk called Hanasaku Ikkyuu, who was famed for his cleverness. He used to eagerly sharpen his mind, solving challenging riddles sent to him, until his mother fell ill. When he found that his cleverness was of no use in helping her, he gave it up.

Karma seeks out Ikkyuu, eager to best him in a battle of wits and consume his soul. One day, Ikkyuu rescued a young beggar boy, only to see him fall ill with a mysterious illness. That same day, Karma finally finds Ikkyuu and offers him his dangerous bargain. Thanks to Karma, will Ikkyuu finally have a way to use his cleverness to help the people around him?