An alternate dimension that is Ezraphel's homeworld. Once upon a time it was your typical generic high fantasy world complete with Magic, other races such as Elves and Dwarves, Gods and Monsters. They all lived by a system created by the Chief God where the monsters would wage an endless cycle of war with the other races in an attempt to rule the world. this would in turn galvanize the other races to join forces against this threat. The Chief God would choose a champion from among her followers to lead a party and kill the Monster Overlord who acts as the leader, ruler and rallying point for the monster army.

This was how it is until over a thousand years ago when a powerful Succubus by the name of Lilith assumed the throne. Lilith was not only a pacifist but held no anymosity towards the ther races and in particular adored humanity. So tired of the system of violence and envisioning more for her fellow monsters she cast a worldwide spell through her own power and authority as the Monster Overlord, embuing anything and everything with Demonic Energy with her own Succubus mana. This had the effect of transforming the savage monsters in Monster Girls with Succubus properties who are less interested in blood and slaughter and more interested in love and sex.

Following this act the entire system was flipped on its head as the enemy of the other races were no longer interested in fighting leading to a fracture of the alliance held by them. The Chief God sent her champion to kill this new Overlord as is tradition however instead the Hero was persuaded to abandon his mission and side with her instead. The Chosen Champion of the Chief God ended up marrying the Mamono Overlord, empowering her through sex and bearing many daughters thus cementing the new world order.

A coloquial term given to the current species of monsters who were changed into Monster Girls through the power of the current Succubus Overlord Lilith. Through Lilith's spell Mamono were granted some her unique qualities which include: 

Body modification to a female form that human men would find sexually appealing.

A high sex drive which is a result from inheriting Lilith's Succubus physiology.

An instinctive drive to find a life partner or 'Husband' and procreate.

The ingrained instinct not to harm others, particularly humans (though this instinct can be ignored through will.)

Mamono are far removed from their savage ancestors in terms of appearance and attitude however they are still inhuman and their thought process is different due to this. As such while they may come off as mostly harmless hopeless romantic nymphos they can be aggressive and unreasonable in their pursuits of love and sex employing all manner of tactics that could be considered amoral so long as no physical harm or permanent damage is dealt...most of the time.

Lilim is the name given to the daughters of Lilith, the Succubi Princesses of the Makai. The name was chosen in homage to Lilith who was the first and Succubus variant of her kind and the original something her daughters inherited. Due to this trait inherited from their mother along with their upbringing Lilims are among the most powerful Mamono in existence, commanding superior sex appeal, magical might and charm abilities so powerful that they could even bend any man (or woman) to their will with but a single glance. They also have an insatiable lust that can only be truly quenched by sex with the man they recognize as their husband.

It was through this power and their authority as royalty that The early generations of Lilim, most notably the eldest nine Lilim went on to become powerful and important figures in Mamono society due to their various achievements and because of the example set by the elder Lilims before them the generation after usually aspire to become Queens, Generals and Sorceresses that would advance their mother's cause. 

It was only in the later/current generations  that they have branched out to other aspirations that have less to do with the war and advancing Mamono cause and more to do with personal fulfillment. Unbeknownst to the public and even their parents this shift in ideology has caused some tension among the siblings.

The 27th daughter of the Mamono Overlord Lilith, Ezraphel belongs to the second to latest generation of Lilim yet despite being among the youngest of her siblings her body is developed to where it is the physically closest to their mother's. Having come at an empasse with her life Ezraphel became disillusioned with the glory and patriotism that came with her station as a princess she left from under the umbrella of her family to explore other options, eventually coming to the decision to just find a worthy husband and settle down.

To this end she poured time, energy and resources into creating a spell that would do just that both as a means to fulfill her desires and also to stick it to her sisters who underestimates her. Unfortunately things went awry when instead of sending her to a place on Eos the spell sent her to another dimension at the home of Stanley Burkowitz.

Well at least the spell works, right?

The short, introverted, beligerent, self proclaimed 21st Century Schizoid protagonist who has deliberately resigned himself to the life of a modern hermit after having a terrible go at handling the real world. Despite this Stanley is resourceful, intellegent and lucky enough enough to win big in life, acquire a job he loves to support the lifestyle he chose. Stanley is a realist, critical of other people and very self aware of himself often to a self depreciatin degree. 

He also may not be all there mentally  after so much time in isolation but that is no longer the case with the arrival of the dimensionally displaced new occupant. The isolation part, as for his sanity well let's just say Ezraphel's presence may just make or break it.

The current Mamono Overlord and mother of Ezraphel responsible for the transformation of monsters into Mamono. A self professed pacifist who is not interested in conquering the other races as her predecessors and wants to integrate Mamono into the world peacefully. She became the direct enemy of the Chief God after she persuaded the Chosen Hero to side with her resulting in their marriage. With his help she was able to become empowered enough to rival the Cheif God in strength and in fact repelled an attempted assassination by the God herself.

Currently she and her husband are working towards completely shattering the Chief God's system by allowing Mamono to conceive male Incubi children as opposed to only famale Mamono babies.