wildcard; storm card; gaji
In hanafuda, a special card that can act as a wildcard or storm card, often called gaji. Used in specific game rules.
In hanafuda, drawing the wildcard makes it easier to complete a yaku.
The extra card in kabufuda often has a picture of an ogre on it.
In this game, the extra card is used as a joker.
株札 is another traditional Japanese card deck that may include an 鬼札.
鬼 (oni, ogre) + 札 (fuda, card). The card sometimes depicts an ogre, hence the name. The exact historical origin of the card is uncertain.