“Huh? What do you mean, Shihon might die? What? She lost her head?”

It seems that Shihon’s headless corpse turned up in the meditation room.

“B-but they can still put it back on for the next forty-eight hours, right? What’s that? They can’t find it?! S-Somebody hid it? You don’t know who? O-Oh, no…”

Murder is not exactly unusual.
Heck, we have our very own serial killer right here at the institute.

Killing somebody is one thing, but hiding her head after is on a very different level.

How are they supposed to come back if you do that?
I can’t believe anyone could have hated Shihon so much as to make an effort to make sure she stayed dead.

If we can’t find her head in the next two days, then Shihon will really be gone!

That’s a future that I just can’t accept!
No more time to be in shock, no more time to cry!

I’ve got to find a way to save her!

“I’ve never done anything like this before, but…!”

I’ll find Shihon’s head, whatever it takes!

“I’ve decided to become a master detective!”

An isolated live-in institution…
With no contact with the outside world…
Home to a population of girls who never die.

Whenever they grow up, they start aging back down until they are babies again, then grow once more in a neverending cycle.

There’s only one way to graduate.
One must be recognized as a genius by some observing entity on the outside.
The moment such an acknowledgement takes place, the girl in question graduates and disappears from the institute.

And so, a sudden murder is enough to turn their immortal lives upside down.

Why do the girls never die?
Why do they grow older, then younger in reverse?
How long have they spent within these walls?
How can they be brought back from decapitation?
What happens to the girls who fail to prove their genius?
What has become of the world outside?
Why is there no one but girls in the institute?
Where are the men?
What is death?
What is life?
Humanity?

For what purpose were we born?

No key to this mystery—but there is a needle.

Wool needle, knitting needle, sewing machine needle.
Silk needle, stitching needle, injection needle.
Futon needle, clothing needle, hook for a fish.
Marking pin, headpin, indicator pin, leatherwork needle.

Follow the needles to your immortal death.