Beside there being potions to become an incubus there is also.
>Also, in some cases, there are those who become “beings who transcend human limitations”, like heroes and incubi, even without the intervention of a god or monster. In such cases, there is something that removes the shackles of humanity, but the person himself will usually not even be cognizant of it. The distinction between incubus and hero is made even more tenuous due to these ambiguous beings who are difficult to classify. An example of a factor that could cause this is remaining in lands teeming with mana for an extremely long period of time. Sometimes legends about such places are handed down with claims like “if you train in this land, you can acquire inhuman power”. It seems likely that the source of such legends is people who acquired superhuman power by continuously training in those lands. For instance, in the case that the location is a land teeming with divine mana, then it can be inferred that the shackles of humanity were removed due to the influence of divine mana, and as such, the person would have transformed into a being who is very nearly a “hero”. On the other hand, training grounds where monsters who seek to master martial arts such as “jinko (Encyclopedia II- p. 168)” and “hinezumi (Encyclopedia II – p.174)” gather are lands teeming with mamono mana, i.e, there is a possibility that they have become mamono realms. Humans who accumulate training in these special mamono realms can acquire power enough to rival monsters, or sometimes even power surpassing that of monsters. In this case, he would become a being very nearly an “incubus”, but either way, the man himself would be unaware of it, and the order wouldn't recognize it either. He would still be treated as “human” in human society regardless, so long as he was lacking a monster wife.
>Other than that, shackles are sometimes removed from being hit by spells. Rarely, there are tales of those who acquired mana over the human limit by having survived after nearly dying from being hit by a big spell. Also, aside from that, if a forbidden degree of healing is performed using the hieromancy spell “miracle of restoration (p.67)” such as regeneration of lost limbs or treatment of deadly diseases, the patient may awaken as a being that is very nearly a hero. In most cases, the factor that caused the unshackling is indeterminable. Among them, there are those who broke the limit themselves by continuously accumulating training even after reaching the human limit, and even those who are thought to have never had any human limitations in the first place for some reason. As expected, these “beings who transcend human limitations” are pretty much the same as heroes and incubi. The only thing that distinguishes them is the fact that they have neither divine mana nor mamono mana in their body. Additionally, if they were to take divine mana within their body by acquiring hieromancy, or take mamono mana within their body by obtaining a monster wife, then there would probably no longer be any way of distinguishing them from heroes or incubi.