According to Japanese folklore, biron are elongated, white, ghostly-looking yōkai with drooping features, protruding teeth, and long tails. They have soft and flabby bodies with a gelatinous consistency reminiscent of konnyaku jelly.

Biron aren’t particularly harmful yōkai. They enjoy scaring humans by caressing the heads and necks of their victims with their long tails. They can be easily dealt with by throwing salt at them, which causes them to vanish.

Biron’s origins are shrouded in mystery. Supposedly, it is the result of a magical mishap. It tried transform into the shape of a buddha by chanting, “Biro! Biro! Biro~n!” But the spell failed, resulting in biron’s strange appearance.

The oldest written record for biron is a 1972 yōkai encyclopedia by Satō Arifumi. Along with its illustration and description, he notes that it is also called nuribotoke. During an interview late in his life, Satō claimed that biron and its magical spell were recorded in a Heian or Edo Period picture scroll. It was later reproduced in an Edo Period booklet containing reproductions of Toriyama Sekien and other artists’ yōkai illustrations. Unfortunately Satō could no longer remember the name of his source book or its whereabouts, and ultimately he was not able to shed any light on its origins before his death. Other yōkai researchers have never found the book he described. Additionally, the ～ character in biron’s name was not used during the period in which it was said to have originated, adding some mystery to his claim. With no surviving older sources, biron is thought to be a creation of Satō Arifumi.