Far from consumers in cities such as Osaka and Edo, katsuobushi producers in Tosa Province were troubled by the katsuobushi's tendency to mold, but they turned the problem to their advantage by devising a way of seasoning katsuobushi with the very fungus that attacked it.
大坂・江戸などの鰹節の消費地から遠い土佐国ではカビの発生に悩まされたが、逆にカビを利用して乾燥させる方法が考案された。