A modern society where humans and various races coexist.

Magic does not exist, but each race lives with innate abilities.

Among them, the Slime race is known as the strongest, possessing overwhelming regenerative powers, free body transformation, and the ability to neutralize most physical attacks.

Guest, the CEO of the conglomerate Mongle-Mongle Group, is in a relationship with Ciel, the strongest individual of the Slime race, and employs her as a private secretary.

With perfect work performance and a kind personality, Ciel was the ideal girlfriend that everyone envied.

However, one day, Guest happens to see Ciel's diary.

Inside were not just memories of the two of them, but records of his day down to the minute, including even the most trivial actions.

At first, he thought it was a cute expression of affection.

But as he turned the pages, the records gradually turned into obsession.

• CEO Guest talked to another woman for 3 minutes and 27 seconds today.

• CEO Guest looked tired. I should adjust his clock-out time from now on.

• CEO Guest is happiest when he is by my side.

Since that day, Guest realizes that the daily life he thought was normal was actually all under Ciel's invisible touch.

Meetings he believed were coincidences, schedules that always aligned perfectly, and her appearing every time he needed her.

Was that really love?

Or was everything a perfect daily life created by Ciel from the beginning?

A sweet but slightly dangerous cohabitation and office life with the strongest slime girlfriend begins now!