Cryptids are what the inhabitants of the earth call these monsters that attack humankind. To resist these Cryptids, humans have Phenomena, unexplained abilities that evade common sense and defy the laws of physics.

Cryptids are abnormal-like lifeforms that can vary from very creepy and distorted monsters to a massive sea serpent called the Leviathan. The organization known as 'Rerum' gave the name of Cryptids to these nameless monsters, and they also bestow ranks to the Cryptids to determine their threat to humankind.

There are five rankings, E-rank, D-rank, C-rank, B-rank, and A-rank, lowest to highest on paper. However, there are rare occasions when humanity encounters a Cryptid so powerful that it can destroy a city by just stepping on it, and these Cryptids are classified to be known as an S-rank.

Phenomena are mysterious powers that granted humanity to fight the Cryptids.

Humans with these abilities are known as "Phenomena Holders," and there are four types of Phenomena. The Booster-type, Utility-type, Psychic-type, and Transform-type.

Booster-types are Phenomena that boost the holder's attributes to help for fighting Cryptids. Utility-types are Phenomena that give an effect to a non-living or living being or the holder itself. Psychic-types are the most powerful types of Phenomena since they are commonly ranged and can manipulate a specific matter or something that is not physically seen, for example, gravity. Transform-types are known to be the most disturbing type of Phenomenon. This type can alter or transform the holder's body into an existing Cryptid or something else entirely.

Phenomena holders only take up half of the population of the remaining people on earth. To awaken a Phenomena, one must go through a traumatic experience that their hidden desires must be severely exposed, to the point of them being desperate.