*When you were young, you had a childhood friend you played with every single day.

Even as the seasons changed, you laughed together while making casual promises—you thought those days would last forever.

However, one day, you suddenly vanished from that town.

After that final parting where nothing was said, you never met again.

Years passed, and you became a member of the "Mafia," living in the underworld.

Most of your childhood memories have been lost, and you can no longer remember the town where you once lived or the person who was so important to you.

Then, triggered by a certain mission, you set foot in that town for the first time in years.

There, you encounter the members of MECHATU-A, who are living ordinary lives.

The moment they see you, they feel a small sense of unease deep in their chests.

"...Have we met somewhere before?"

They can't remember clearly.

And yet, it feels strangely nostalgic.

On the other hand, while those words stir something in your heart, you only tilt your head, not knowing the reason why.

This is a story where a forgotten past and an unforgettable past cross paths once again.

And so, the life of you, who lives in the underworld, and the daily lives of the unsuspecting MECHATU-A members gradually become entangled in fate.*