Bizarre humanoid monstrosities called INKlings appear as antagonistic forces in Haruki Murakami's Hard-Boiled Wonderland and the End of the World. Lurking in the dark below, the Calcutec must navigate across their territory.
For the most part in the Hard-Boiled Wonderland portion of the narrative, the INKlings are unseen creatures dwelling in the subway tunnels, sewers, and other underground sections beneath Tokyo. There are accounts of sewer and subway workers that mysteriously disappear, as though carried away by something malignant. The Calcutec first hears of them when making his way to the Professor's underground base which is deep within INKling territory although the creatures themselves are repelled by sound-waves produced by the Professor's machinery.
They persist as a threatening force, taking advantage of the darkness and humanity's weak-to-nonexistent night vision to do as they may-although they will never go above to the surface and flee any lights shone in their direction. On a much more menacing level, it is revealed that the INKlings have a base under each major governmental building in Japan, thereby using them as leverage. Should anyone in Japan attempt to exterminate or remove the INKlings, they will drag every governmental official into the darkness below.
When the Calcutec has his apartment raided and ravaged by two thugs, the smaller describes the INKlings as being like the "Kappa" of Japanese folklore. Further information is provided by the Professor's chubby Granddaughter in that the INKlings prefer to drag away human prey and leave their bodies to decompose in the sewers before consumption. They also speak a language that is described by the Granddaughter as vulgar.
Later on in the narrative, the Calcutec must consult the Professor about the experiment performed upon him and is helped by the Granddaughter to find him. They use portable INKling-repelling devices and find that the Professor's underground base has been broken into. They receive information from the Professor who notes that they must go on, saying he'll make his way back on his own. It is revealed that the INKlings have worked with the Semiotecs, a terroristic group seeking dominance in Japan's information war. As they move further to find the Professor, the Calcutec and Granddaughter stumble across a temple indicating the INKlings' culture and religion. There, they worship a fish entity with no eyes and there are leech pits wherein some unfortunate victims are sacrificed. The Calcutec and the Granddaughter barely avoid a rush of INKlings that try to take them. The two make their way into a subway tunnel, the Calcutec noting the abandoned shoe of an INKling victim.
As that is the final time the INKlings ever appear in the narrative, it can be assumed that they are still everpresent beneath the Hard-Boiled Wonderland incarnation of Tokyo and carrying away unfortunate workers.