Both canine sidekicks are usually depicted as floating dogs whose bodies trail off into stylized mist where their hind legs and tails should be. This is probably intended as a visual indication of the fact that they aren’t just yokai–they’re ghost yokai. In a two-part episode about ten or twelve installments into the anime, it’s revealed that centuries ago, Madarao–and presumably Tokine’s “dog” as well, although a lot less detail is provided about him–were what appear to be supernaturally strong and intelligent wild dogs (at least, that’s what the translation calls them–they seemed more like wolves to me) who wound up being killed after repeatedly attacking the humans who kept encroaching on their turf in the wilderness that eventually became Karasumori village. After Madarao died and was converted into his more insubstantial spirit form, Yoshimori’s ancestor managed to win him over. I’m not sure exactly how Tokine’s “dog” became her clan’s designated assistant, since the two-part episode focused mainly on the ongoing conflict between Madarao and a fellow canine ghost-yokai from his old pack, who retained his bitter enmity toward humans in the afterlife and attacked Madarao when he couldn’t persuade his old friend to join him in killing the humans and taking over Karasumori.

There’s also another “shaman’s best friend”-themed manga, Mick Takeuchi’s “Her Majesty’s Dog,” published in the U.S. by the now-apparently defunct Go!Comi. This series is about a teenage girl named Amane who is the heiress to a long line of practitioners of kotodama (a specialized form of spoken-word magic that involves controlling people and things by using their true names) who normally operate out of a remote rural island. When the sheltered Amane persuades the clan elders to let her come to Tokyo to attend high school, her shapeshifting koma-oni familiar, Hyoue, a formidable canine yokai who can take the form of a slightly punk-looking teenage boy, comes with her. Hyoue is even more devoted to his mistress than Tokine’s “dog” is in “Kekkaishi.” In fact, he’s in love with her. (Hyoue tries to hide this, but it’s obvious to just about everyone but the naive and socially isolated Amane herself.) This violates all the rules of how such human/koma-oni contracts are supposed to work, incurring the disapproval of the clan elders, who at one point actually attempt to break the bond between Hyoue and Amane.

Yokaiden: This charming OEL manga drawn by Nina Matsumoto is about a boy who loves yokai so much that even after his grandmother is killed by one an he sets out into the yokai realm to find her killer, he still manages to make yokai friends left and right! His cheery, if naïve, nature and non-discriminating attitude just attracts a lot of yokai helpers in his quest. The fact that some may be taking advantage of his good nature does not seem to cross his mind.

Naruto: I’m not sure if it counts, but it is worth mentioning that the Nine-Taile Fox Spirit, usually considered a yokai or other type of demon in Japanese lore, resides within the title character.This made him an outast in his village as a child, even though he is able to control the Fox’s destructive power-most of the time!