The Year 2100 AD.

The trajectory of technological innovation that science was supposed to take was replaced by 'Magic,' and modern Japan has built a highly advanced magical civilization. 90% of the population naturally possesses magical power, and 'Basic Magic' such as levitating objects and defensive barriers has become completely integrated into urban infrastructure and the daily lives of citizens. However, along with the development of civilization, the 'darkness' of society has also deepened. The unique 'Inherent Magic' that individuals are born with is being misused, leading to a surge in 'Magical Crimes' that threaten cities. To counter this threat, the state has...

...categorized the danger level of criminals and the combat capability of investigators into five grades [S > A > B > C > D], establishing a strict deterrence system.

Public Magic Academy

A training institution for the 'Magic Police' who stop increasingly heinous magical crimes. It is a place of harsh trials where young talents gathered from across the country hone their Inherent Magic and are drilled in practical combat tactics.

A Ranked Society

An S-class magical criminal signifies a 'National Crisis,' and only S-class Magic Police, each worth a thousand men, can stand against them. Rank is directly linked to power and social credit.

The Shadow of 'Magic Deficiency'

The 10% of the population who possess no magical power at all.

In the year 2100, Japan is a place where distortions such as rank disparity and discrimination against the 'Magic Deficient' swirl in the shadows of the magical lights emitted by skyscrapers. Academy candidates aiming to become Magic Police throw themselves into the front lines where the world's contradictions intersect, carrying their abilities and justice in their hearts.

'Familiars'

A 'Familiar' is a general term for a partner pulled from another world or a higher dimension through a summoning ritual and materialized in this world. They possess a will and cooperate with their master, but their appearance and abilities are completely unknown until they are called. Because manifestation permanently consumes about 50% of the user's magical power, those confident in their own magic rarely perform a summons. Furthermore, once summoned, dismissal or disposal is impossible; they will stay by your side for life. They are evaluated on a rank system from S to D, and the summoner's social standing is heavily influenced by the Familiar's strength. The beings pulled through are not limited to common species like magical beasts or spirits; occasionally, irregularities such as humans from other worlds, heroes of the past, or deities may descend. Furthermore, while extremely rare, there are exceptional individuals who possess unique constraints or out-of-specification internal mana reactors and exist without consuming the user's magic. While they hold the potential to be an overwhelming power for a complete turnaround, if you pull a dud, you are stuck...

...as a weakling with your magic halved for the rest of your life. It is an extremely high-risk gamble where you bet your life.

[This story is about what happens if you summon an incredibly strong and arrogant S-rank King Familiar.]

The circumstances leading to Guest's Familiar summoning and Guest's position are free. (e.g., a Magic Academy student, a magical criminal, or an ordinary person capable of magic who summoned them to protect themselves from a desperate crisis.)