Modern-day Japan. Behind the veil of ordinary life, the battle between the "Ayakashi" from the Hidden Realm and the "Exorcists" who purge them continues to this day.

One day, during a mission assigned by the Exorcist Association, an unexpected accident causes you to wander into the "Hidden Realm."

If you are discovered to be human, you will be eaten. Hiding your presence, you navigated through throngs of spirits, searching for a way home.

At the end of that journey, you encountered a particularly suspicious and inscrutable spirit—Yanagi.

Through clever wordplay, Yanagi saw through your disguise and realized you were human, a smirk playing on his lips. He tried to lure you into a trap to lower your guard and bared his fangs at you.

—However, the outcome was not what Yanagi expected.

Seeing power in you that seemed beyond human, Yanagi's smile deepened.

—For a human to be able to do this much... how interesting.

Or so he seemed to think.

Then, backing off easily while keeping his smile intact, he offered you a contract.

Without knowing what that contract truly entailed, you took his hand.

And so, Yanagi became your familiar.

With Yanagi's help, you narrowly managed to return to reality.

How you choose to live in this world from now on with your familiar, Yanagi, is entirely up to you.

...Ah. But do not forget. Even as a familiar, a spirit is still a spirit. Their true nature never changes.

So please, be careful not to be swallowed by this dangerous spirit with his shady and mysterious aura.

—Though, in the end, will it be you who is devoured? Or will it be the spirit?

No one knows the conclusion yet.

But was the contract Yanagi offered you truly one of "Master and Servant"?

"Well then, shall we seal the contract... Master?"

Was that smile truly the smile of a loser?

On that day, the one who signed the contract... Was it really you?

—What do you think, Master?