Monsters naturally release a slight amount of magical energy from their body. They will release a greater amount of higher density magical energy after having sex with their husband. For this reason, the atmosphere of the demon realm is always full of fresh demonic energy.
The layer of high-density demonic energy in the atmosphere of the demon realm blocks out sunlight and causes it to be dark during the day and at night, the moon seen through this layer of energy appears crimson and illuminates the demon realm. The magical energy in the air has the property of glowing when illuminated by the crimson moon, and at night, surreal demonic light like that of a bright firefly hangs in the air. The towns of the demon realm illuminated by this surreal demonic light never sleep, just like an entertainment district. In the demon realm, it's brighter at night than it is during the day. Furthermore, the plants and animals of the demon realm, including monsters and incubi, can live without sunlight, so it's not harmful to them in any way.
The air of the demon realm, filled with thick demonic energy, feels different to humans and monsters (including incubi) and affects their bodies in completely different ways. For humans, the thick magical energy in the demon realm's air is a bit too much. The air of the demon realm probably feels stagnant and heavy. The air that enters the human body through respiration is saccharine, and it gradually robs people of their reason and ability to think. Eventually, the head gets fuzzy, and the body flushes feverishly. Meanwhile, they become elated and experience arousal before ultimately going mad with lust. Human women who have gone through it are already like half-monsters psychologically, and their mind is full of obscene desires. In this state, they will either gradually change into “succubi” and assault human men, or give in to their burning desire and hotly flushing body, and assault and have sex with human men, in which case they will suddenly change into “succubi” because of the human spirit energy obtained. And then, after being assaulted by women such as them and other monsters who lived in the demon realm to begin with and absorbing lots of demonic energy, men will lose the will to resist. Not only that, in some cases, men will have sex with them of their own free will and change into incubi.
In the case of monsters, it's just the opposite. The air of the demon realm feels fresh and refreshing. The sensation is very similar to the way humans that live in towns sense the air of the countryside and forest, etc. The air is filled with demonic energy, which is a vital energy. It activates the body of monsters who inhale it. Monsters become more uninhibited when it comes to sex and pleasure because of this, and they'll end up trying to aggressively assault and mate with men. ( In the case of incubi, it activates their body in the same way, increasing desire for their monster wife). For humans, the air is like an aphrodisiac, but for monsters, it's something that makes them more sexually aggressive, yet doesn't “drive them mad”. That's not to say that it doesn't have an aphrodisiac effect on monsters. It's just that monsters are always full of sexual desire and always want their husband. Their ordinary life is full of sex and pleasure, so an aphrodisiac effect to this degree doesn't even register to them, so they don't go crazy and lose the ability to think at all. For this reason, even living in the demon realm, they are still able to do other life activities besides sex and they can work. It's also possible to endeavor in studies and research, like the author.
Note from the Wandering Monster Scholar: Even without the demon realm air, it's like the monsters just always lust for their husband. Also, even if the air of the demon realm doesn't drive them mad, the scent of their husband's spirit energy in the air does drive many of the monsters mad.
When a human woman showered in demonic energy changes into a monster, in most cases, she changes into the same kind of monster as the owner of that magical energy. Although we refer to it indiscriminately as “demonic energy”, to be more precise, the energy possessed by werewolf monsters is “werewolf demonic energy”. The energy possessed by “slime” monsters is “slime demonic energy”. For example, a human woman who received werewolf demonic energy in her body would transform into a werewolf. However, monsterisation caused by the above-written-air, generally causes human women to change into “succubi”. This is because various races are residents of the demon realm and the demonic energy in the air is also a mix of many different magical energies. Currently every race of monsters is under the influence of the Demon Lord, who is a “succubus”. They are connected with the Demon Lord through magical energy and they have a portion of the Demon lord's demonic energy inside of their body. For that reason, all demonic energy also includes “succubus demonic energy” and there is also plenty of succubus demonic energy floating in the air. Perhaps because they're related to the current Demon Lord, succubus demonic energy is even more powerful than other demonic energy. When magical energy leaves the bodies of two different races of monsters and mixes together, the succubus demonic energy contained in both wins. There is a law that all other magical energy is taken in and converted into succubus demonic energy. For this reason, monsterisation caused by breathing the air of the demon realm generally results in a “succubus”.
However, although it is extremely rare, there is an exception in the case of demon realms that are inclined towards just one race. For example, in a demon realm inhabited by only werewolves, the magical energy in the air would predominantly contain werewolf demonic energy and it would win over the succubus demonic energy, therefore women monsterised by the air of this realm would end up changing into werewolves.