Unicorns are centaur-family monster girls remarkable for their distinctly good-natured behavior. Gentle monster girls that reject the screw-everything-that-moves nymphomaniacal attitude of the succubi and most other monsters, they guard their own chastity and prize it in others too, giving them a particular fondness for virginal husbands. While they will wait for marriage, the release of their pent-up lust on their wedding night is remarked as "ferocious".

Still, unicorns are monsters, and a monster's desires often overwhelm their better judgement. Erratic sex with a man who has another monster's energy on him causes a dramatic physical and mental transformation in a unicorn, turning her into a bicorn. A husband needs to remain faithful in order to keep his unicorn wife from transforming. Although the only downside is the husband will slowly tranform into a unicorn as he continues to remain faithful and have children with her. 

Encyclopedia Entry

A type of centaur that lives deep in forests, distinguished by its beautiful white coat and a single horn coming out of its forehead. Even though it’s a monster, it is regarded as a “symbol of purity.” Its graceful personality gentle behavior are that of a chaste maiden.

Unicorn extra art

They are the symbol of purity, but in a manner befitting of their true nature as a lustful centaur family monster; their first kiss will involve the insertion of the tongue and the exchange of saliva, and later their kisses will become even deeper and wetter.

In the same way as other monsters they make the man they like their husband and produce children by him, but unlike other monsters, they never attack and force intercourse. It is said that the men they are fond of and choose as their husbands are absolutely limited to pure “virgins” who have never had intercourse with other women or monsters. They themselves stay as pure “virgins” and never have sex with any men until they give themselves to their husband. They never give themselves to any man but their husband period. Sex with their man is the fulfillment of the oath between husband and wife.

Because they possess this sort of nature, they tend to be misunderstood, but just like other centaurs they are extremely lustful. Unicorns without husbands spend their time dreaming of days of sweet pleasure with their husband to be. When they swear their oath to their husband, in order to make everything they have dreamed of a reality, they'll use their lewd body they have been saving just for their husband to thoroughly service him. Afterward, they'll frequently seduce their husband and spend sweet days of pleasure continuously having sex just as they dreamed.

There is powerful demonic energy contained in a unicorn’s horn and because of it, they can use powerful healing spells. This healing power grows more potent the purer their “unicorn energy” is. Conversely, if another magical energy gets mixed in, it loses power. It is said that this is the reason why they avoid men who have had intercourse with other monsters, in order to prevent the magical energy of another monster from mixing in with their unicorn energy.

A unicorn's own demonic energy protects it against demonic energy from the outside, so it normally causes no problems. However, if her husband cheats on her and demonic energy from other monsters accumulates in his body; or if she has sex with a man who has had sex with monsters many times instead of a virgin, then she'll be helpless to prevent it and demonic energy will be poured inside of her.

When that happens, a unicorn's energy becomes radically distorted and she will transform into a monster called a "bicorn", which in contrast to the unicorn, is referred to as "the symbol of impurity". They regard indecency as virtue and desire to live an obscene life even more immersed in pleasure together with their husband. Because of this they'll even call the person their husband was cheating with and then in order to obtain even deeper, more intense pleasure, they'll have threesomes together.