Jinmenkens (Jap: 人面犬) (Also called 'human dogs' or 'HFDs') in the Thunder Series are a race of dog-like animals who stereo typically live not far away from modern or urban areas. Different variants of this being exists within specific regions depending on the climate.
Jinmenkens live in communities near that of Neagi Wolf territories and are thus a major role in the series as a being. Some are noted to have even played a role in the population.
Jinmenkens are of course designed entirely off of the jinmenken from Japanese urban legends. They are a dog-like being with a humanoid face. They come in two different categories which are corporeal and incorporeal. Jinmenkens come in any breed that dogs with regular faces would and it shows in the series; it's believed that they hold a link to Proto Dogs of that breed.
Corporeal jinmenkens are dogs who exist as a soul within a completely solid body, just like other living creatures. Most of them originally being ordinary humans from a past life. Currently known corporeal jinmenkens being Lance, Shiloh Boone, and Timber (partially).
Incorporeal jinmenkens are entities who are not composed of solid matter and therefore cannot be touched, nor can they physically touch anyone else but are, however visible to everyone. The only known incorporeal jinmenken is Nikumenken.