Oseichu – The Mimicking Roundworm


Translated and Sourced from Mizuki Shigeru’s Mujyara, Japanese Wikipedia, and Kaii Yokai Densho Database

It starts with a high fever and some stomach pains, and ends with a giant mouth poking out of your own stomach, speaking in your own voice demanding food and drink. It’s bad enough getting sick, but you don’t want to catch a yokai disease. Especially you don’t want to get infected by an oseichu, a mimicking roundworm.

What Does Oseichu Mean?

Oseichu is made up of three kanji – 応 (O; affirmative, agreements ) + 声 (sei; voice) + 虫 (chu; worm, bug). The three kanji translate roughly into “Voice Mimicking Bug,” all though the word “bug” refers more to the infectious disease type than the insect type.

The term osei (応声) is really only used in relation to this yokai. In fact, sometimes the “chu” is dropped altogether and it is just called an osei.

The Oseichu of Chusaburo

This is a story from the 16th year of Genroku (1703 CE). The laborer Shichizaemon lived with his family in Tokyo. One day, his son Chusaburo was struck down with a terrible fever and pain in his stomach. The illness continued, and after a few days they could see a boil growing form the son’s belly. The boil kept growing larger and spreading until it resembled a massive, human mouth. Everyone in the family was shocked when the boil finally opened its mouth, and began speaking in Chusaburo’s own voice. The voice began demanding food, and anything shoved into the giant mouth soon disappeared. The mouth was never satisfied and demanded more and more food, while Natsaburo was slowly starving to death, deprived of sustenance.

Shichizaemon tried every medicine he could find, and summoned exorcists and sorcerers of all type to help the misfortune of his child, but to no avail.

At his wit’s end on how to help his son, Shichizaemon sent for the famous doctor Kan Gensai. The renowned physician took one look at Chusaburo and declared that he was infected with an Oseichu. Dr. Gensai whipped up a special blend of six medicines, and fed them directly into the extra mouth protruding from Chusaburo’s belly. After the first day, the mouth ceased to speak and the boil reduced in size. By the second day, Chusaburo expelled a giant worm from his anus—33 centimeters long. The worm looked like a lizard, with an arrow shaped head and long body. It tried to run away, but everyone in the room immediately set upon it and beat it to death.

With the Oseichu expunged, Chusaburo made a complete recovery.

Yokai Diseases and Mysterious Bugs

The oseichu is thought to have come to Japan from China, where there are similar stories based off of real-life parasitic worms like roundworms. Oseichu is a good example of how yokai can be many things, from giant, one-eyed monsters down to strange, infectious diseases. Oseichu are not a type of monster, but are considered a type of kibyo (奇病; Strange Illness) brought on by kaichu (怪虫; Mysterious Bugs). It is easy to see how roundworms can become yokai. A sudden fever and feeling of hunger, finishing with a large worm being expelled from the anus—that must have been terrifying to those who weren’t aware of what was happening.

The oseichu is found in three Edo period collections; the Shin Chomonju (新著聞集; New Collection of Famous Tales), the Shiojiri (塩尻; Salt’s End), and the Kanden jihitsu (閑田次筆; Continued Tales of a Fallow Field).

Both the Shin Chomonju and Shiojiri tell tales similar to The Oseichu of Chusaburo, with only slight variation. Shin Chomonju sets the story in Tokyo, while Shiojiri says the mysterious illness occurred in the Abura no Koji district of Kyoto. Shiojiri also says the medicine took 10 days instead of 2.

The Kanden Jihitsu tells a similar, but different story. In the 3rd year of Genbun (1738) , a side show manager running a Misemono (Seeing Things) show in Tamba province (modern day Kyoto) heard a rumor about a woman infected by an oseichu. He immediately went to her house to attempt to recruit her for the show, and was stunned to find an authentic case of the disease. An unmistakable voice came from the woman’s belly. The woman’s husband was ashamed of her condition, however, and would not allow her to be displayed. The disappointed side show manager went home empty handed.

Translator’s Note:

It’s November, and that means Thanksgiving Day in the US! And Thanksgiving Day means eating so much your stomach hurts afterwards, and that got me thinking about Oseichu.

Oseichu is an odd yokai. It doesn’t appear very often in yokai collections. I would like to that’s because it is gross, but yokai have never let being gross bother them! This one is clearly a supernatural version of a natural disease/parasite – the roundworm. Something I hope I never have to experience in real life!

Further Reading:

For more bizarre yokai, check out:

Jinmenju – The Human Faced Tree

Inen – The Possessing Ghost

Kejoro – The Hair Hooker


4 Comments (+add yours?)

  1. Joseph Barrett
    Nov 18, 2013 @ 23:14:02

    Kind of reminds of the Futakuchi-onna will that it’s a parasitic mouth demanding food


  2. Sarah
    Nov 19, 2013 @ 03:56:20

    Yuck! 🙂


  3. 83n831
    Nov 19, 2013 @ 08:33:28

    This is a Japanese version of the internationally distributed legend type often classified under the title “The Bosom Serpent” (after Nathaniel Hawthorne’s 1834 short story that makes use of the American version). Folklorist Gillian Bennett gives a useful summary of international variations on the theme in chapter 1 of her book “Bodies: Sex, Violence, Disease, and Death in Contemporary Legend” (Mississippi, 2005). The voice element is distinctive, but many versions feature the indwelling creature hissing (as in Hawthorne’s tale), barking, or croaking from inside.

    It’s also interesting that one of the earliest European versions (recorded by the pioneer French physician Ambrose Paré in 1561) describes a Normandy peasant woman who exhibited herself as a kind of sideshow, exposing her midriff and showing spectators how the snake wiggled around inside her. She made a good living at it, as the story made everyone feel sorry for her, “in addition to which,” Paré notes, “she put on a good show.” That’s an interesting parallel to your last example, in which the Japanese sideshow manager seeks out a case to display, but, alas, it’s a genuine case and not a good carny fraud like the one Paré witnessed.


  4. Worm Story
    Feb 12, 2014 @ 12:50:19

    Ha, that’s a cool story. Does it have any relation to the Jinmenso?
    The part about the worm expelling from the anus and being killed then reminds me of the common folk remedy/joke regarding the treatment of tapeworms;
    First one starves the worm, then one puts a piece of food near the exposed buttocks and when the worm comes crawling out one hits it with a hammer.


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