EX04 Tell me, Higashiō. About the immigrant convoy.

"Higashiō, please! Help me with my homework!"

On a certain day in the fourth year of elementary school.

Mio sent a humid gaze toward Maki’s words, delivered with the force of a prostration.

"Again?"

"Please!"

Begged, Mio began counting on her fingers, then stopped.

She no longer remembered how many times she’d heard those words.

Only certain that it was more than the number of fingers she had.

"Torayu, you always copy homework, but that’ll cause trouble during tests, won’t it?"

Trouble, or rather—how many times had she cried from being troubled? Mio started counting again.

This one was clear. Every year, mid-term, end-of-term, and final exams—three per year.

Since she was now in fourth grade, that made eighteen.

This one was barely fewer than her fingers. At this rate, it might not be enough.

"Fine, fine. What part don’t you understand?"

Sorry... I owe you one...

You said that before, didn’t you? That you’d live by your reflexes alone.

Mio suddenly recalls a line from Kō some three years ago.

It might have been a reaction to Emissa’s provocation, she thinks.

Then why are you studying so hard now?

She doesn’t want to boast, but Mio’s grades are top in the school. Naturally, she’s placed in the highest academic track.

If Kō hadn’t insisted on staying in that class, he wouldn’t have struggled so much.

She doesn’t want to say it, but his grades are stretched thin just to be in this class.

Why? Well... lots of reasons. Just lots.

Lots.

Anything goes! But tell me—what’s the structure of the immigrant fleet? I don’t get it at all.

You didn’t listen in class, did you?

◆ ◆ ◆

・Immigrant Fleet

The current human habitation domain.

One solution born from the crisis awareness following humanity's escape from a desolate home planet 150 years prior—on the brink of extinction.

A philosophy devised to prevent total annihilation by dispersing fleets of million-person-capacity migration vessels across the cosmos.

In standard migration fleets, the General Ark-class vessel is designated Ship 1, with Ark-class vessels assigned as Ship 2 and onward.

Inside migration vessels, movement via hypoloope systems is the norm; automobiles are subject to high taxation.

Giant cables connect each vessel to facilitate transit between ships.

Some vessels feature established transportation and distribution networks, including hypoloope tubes and roadways.

Currently, four fleet groups exist—First to Fourth.

With recent population growth, the Fifth Fleet Project has been initiated.

The fleets are positioned in separate sectors of space.

Etheric communication allows instantaneous transmission, but physical travel between them requires repeated overlight jumps.

As a result, regular courier vessels are dispatched, and movement between fleets is possible only through their use.

To date, only one courier vessel has gone missing.

Each fleet operates under its own legal framework; customs shift with the fleet.

For example, mechanical augmentation of the body is legal in the Second Fleet, but illegal elsewhere.

In the Third Fleet, nanomachine-based body management is standard; in the Fourth Fleet, cybernetic integration has created a highly informationized society.

The First Fleet regulates all technologies affecting the body, and is considered naturalist in orientation.

The agreement designed to reduce friction among the various fleets is the Migration Fleet Charter.

Disposal of personal combat equipment serves as a representative example—meant to prevent a scenario in which humanity, having waged war upon itself, would finally face extinction.

The ultimate objective is settlement on planets free from ASID incursions, yet this remains unattainable due to the excessively vast range of ASID habitation.

• Ark-class Migration Vessels

The first migration ships used when humanity first emerged into space.

Approximately ten kilometers in length.

The upper half comprises living modules; the lower half, industrial modules.

Habitable capacity of around one hundred thousand individuals.

Fundamentally designed to sustain interstellar travel independently.

However, when organized as a migration fleet, roles are divided among individual vessels, rendering solo interstellar travel practically impossible.

Used for approximately six hundred years on the home planet, its durability and reliability are beyond question.

A super-large-scale Ether Reactor, designed for the inhabitants, is installed.

During normal operations, it deploys an Ether coating to withstand debris asteroids and similar hazards.

Even so, debris and similar material occasionally adheres.

For this reason, a thorough cleaning is conducted roughly once every ten years.

Rumors claim it is polished until it shines brilliantly.

• General Ark-class colonization vessel

A large-scale colonization vessel constructed after leaving orbit.

Approximately one hundred kilometers in length.

The Ark-class can, if required, descend to a planetary surface and function as a mobile colony, but this vessel is entirely designed for space use.

The Ark-class is further subdivided: the upper section comprises residential blocks, the middle section industrial blocks.

The lower section is the mother ship—a large construction block captured from an ASID Queen-type vessel.

Maintenance for the defense fleet guarding the immigrant convoy, as well as the Ark-class immigrant vessels, is conducted by the lower-level mother ship.

The General Ark-class vessels themselves are divided into multiple modules, each constructed aboard the mother ship.

Without the mother ship, no other vessel can undergo overhaul—eventually, they will sink. It is thus the central core of the immigrant convoy.

Habitable capacity: five million.

All ships except the First Convoy are designated Ship One, housing centralized administrative functions.

Conversely, without Ship One, the convoy cannot maintain its structural integrity and will disintegrate.

◆ ◆ ◆

"Understood?"

"Saved me, Tōgō! Even reading the textbook didn’t make it clear."

"Just memorize everything."

"No, normally you can’t do that..."

Mio looks away, caught in Shu’s expression—half-amused, half-astonished.

“You can do it if you study hard enough.”

“Huh… I’ll try my best, I guess.”

Seeing Mio’s face, pouting with quiet anxiety, Shu hastily reassures her.

In truth, failing to memorize will mean tears during the next test.

I’ll push through, Shu resolves inwardly.

He doesn’t like studying. But since the person in front of him loves it, there’s nothing to be done.

From the moment they met, Shu has felt uneasy—always thinking he must protect her.

So now he pushes himself, studying desperately to catch up. Yet sometimes, Shu wonders.

—Maybe she doesn’t actually need my help at all.

That thought brings a faint ache.

Still—

“Ah, right. Have a good year, Tōya-kun.”

The mere fact that he felt a surge of motivation just from hearing those words made him mock himself—too easy, he thought.