A Keukegen appears on the counter of the arms dealer, Cumberbatch.
Cumberbatch warns a curious Bo, when she lifts the bell jar covering it, that "without a gas mask, it would be deadly."
Keukegen is a creature illustrated in Toriyama Sekien's "Konjaku Hyakki Shūi" (published ca. 1781). It resembles a small dog covered entirely in long hair. Its name is a pun - when written with different kanji, keukegen means "an unusual thing which is rarely seen". According to one report, the keukegen is a disease spirit which lives in damp, dark places and causes people in the house to get sick.