Encyclopedia Entry
A kind of beastmen that originate from pet dogs bound to their masters by deep love that desired a body more suitable for serving their master, and due to this, transformed into monsters after being showered in mamono mana. Since they were originally dog animals, these beings are close to beasts, and their entire bodies are covered in fur. Since they monsterized due to a desire to wholeheartedly serve their master, they are extremely loyal, and it wouldn't be an exaggeration to say that everything they do is for the sake of their master.
After becoming a monster, their excellent olfactory sense can discern more than just odors. They become able to sense when danger is approaching their master, as well as hostility from foreign enemies. With the powerful and nimble body of a beast, they can protect their masters from all sorts of threats. They are highly intelligent, and loyal to their master's orders, and if instructed, they can master most things including: using human weapons and tools, reading and writing, and cooking food suitable to human tastes.
Among them, there are even some cu sith that have become diligent scholars with a command of sorcery for the sake of their wizard masters. Also, they say that some cu sith are so well versed in etiquette due to their royal masters that they behave in such a refined manner that they can be mistaken for being nobility in high society.
In this way, they can be more than just mere watchdogs, and they possess the qualities necessary to become excellent knights and attendants. But no matter how much they serve, they never demand a reward, just getting praised and petted by their master seems to be enough to make them happy from the bottom of their heart. It is said that due to such praiseworthiness, most masters prefer to keep them by their side, and will end up showering them with even more love than when they were ordinary dogs.
In this way, they are intelligent and obedient, but as one might expect given the fact they were originally beasts, they harbor powerful bestial urges. When they become monsters, their body that is made so that they can serve their master will be a female body for the sake of bearing their master's offspring. Whenever they feel the warmth of their master or have their nostrils tickled by his scent, their body will throb, delightfully hungering for his seed. If pursued by their master, they would gleefully offer their body, but as long as it's not what the master desires, they themselves won’t attack. For instance, even if their lust swells up so much that the slovenly expression of a bitch in heat with enraptured eyes and a tongue hanging out appears on their face, out of loyalty for their master, they will continue to bear it with determination.
However, regardless of their will, since they're a beast, their body will release pheromones towards the male once they are in heat. The pheromones will appeal to their master's male instinct, informing him that there's a bitch in heat ready to mate at any time that can be exclusively his. Once a man's male instinct recognizes the cu sith as a female, naturally he'll start to lust for her, and his penis will tower for the sake of impregnating the female.
If they both continue self-denial in such a state, eventually their lust will turn into bestial lust, and reason will be unable to suppress it. The two people will turn into two dogs. Under the domination of bestial lust, the master will mount the female just like a male dog, and forgetting even language, he'll indulge in the female’s flesh, violating her by violently banging his hips against her. Meanwhile, the bitch will realize that she's being used entirely for the sake of her master, and experience instinctive joy for having her body and heart dominated by her master, and she'll also forget language, only crying in an alluring manner to arouse the male’s bestial lust even more and swaying her hips to guide his manhood even deeper inside.