Nigawarai are a yokai (or monster from Japanese folklore) that appear as an ugly, hairy creature with horns. Dressed in dirty rags, their mouths are held in a forced smile. These creatures feed off ill-humour, forced amusement and uncomfortable laughter. In turn, they cause ill-will, disgust and arguments in people and the environments they inhabit. The name nigawarai translates as 'bitter smile.'

Oda Yoshi
These yokai are often blamed for the bad things people do (for example, laughing at the misfortune of someone you hate) in a similar way that the expression 'the devil made me do it' is used in the West. Originally depicted on monster scrolls during the Muromachi period, their significance developed over time with suggestions their poisonous claws could even be used medicinally.