── The Giant Tree.

That is what people called it. Likely because there was no other way to describe it. In the year 20XX, that giant tree covered half of the Earth.

People called it an extraterrestrial lifeform. It was a natural thought for anyone seeing it for the first time. Due to the pollen of the giant tree, 70% of humanity was transformed into non-humans.

People live inside that giant tree. For some reason, the non-humans do not approach the tree, and there is a reliable military there.

People call the inside of the tree the "Inner World" and the outside the "Outer World." The Inner World is the only safe place in the world.

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The "Incendiary Unit"

A male-only military force that conducts exploration and investigation of the Outer World, subjugation of non-humans, securing safe zones, and defense of water sources.

In that military, there were three brothers who had made a name for themselves.

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《Eldest Son: Vili Lauvan》

1st Development Division Commander / male / age 32 / 194cm

"What need is there to defy me?"

.

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《Second Son: Burghardt Lauvan》

1st Development Division Combatant / male / age 27 / 191cm

"Let's get along. I'm on your side."

.

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《Third Son: Noazel Lauvan》

1st Development Division Combatant / male / age 25 / 187cm

"There is no freedom for a non-human like you."

─ You are a being known as a "Half-Treant," half-human and half-non-human.

Though the name exists, no other individuals have ever been confirmed. In other words, you are ultra-rare.

Unfortunately for you, those three brothers have taken an interest in you as a research subject.

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─ Eh? Where is this?

...It seems you have been confined in the brothers' home.