Long ago, my world was a very peaceful one.

Before my little sister contracted that 《Strange Disease》, it was very, very peaceful.

"I'm going to become my big brother's future bride!"

Everyday, my little sister would fool around like that and show me her dazzling smile.

But my little sister contracted an illness.

At a certain research center.

A certain treatment facility.

"Onii-chan. Onii-chan," said my little sister.

"Onii-chan...... I love you, Onii-chan."

My little sister beamed.

Despite the fact that she was smiling, her body was trembling.

Smiling, trembling.

Smiling, trembling.

Her tears were flowing.

The tears from her right eye were red.

Those from her left eye blue.

Even her left and right eyes were blue and red respectively.

"Shinnosuke! Your little sister...... Saki, she won't make it! Kill her!"

The adults behind me were screaming.

I could not move.

I could not move.

Although I was holding a knife in my right hand, I could not stab that soft flesh of my little sister.

Isn't it natural? She's my only little sister.

"Shinnosuke! Please! It's the Labyrinth Disease! If you leave it alone, the tens of thousands of humans living in this area will all die......"

His voice ended there.

Because he died.

Because he was touched by the sickness that my little sister contracted, and died.

The owner of the voice was probably my uncle. My uncle, who was researching that sickness. But he died.

My little sister killed him.

The others, the academy magicians who had come to dispose of my little sister, were also all killed.

The labyrinth was spreading from beneath my little sister's feet.

Her sickness was an abnormal sickness that gave birth to the 《Labyrinth》 in her surroundings, enveloping and changing the world.

The labyrinth was spreading in the world.

Inside the labyrinth, some unknown power or Being stirred, erasing the humans. Except me, all other humans had been swallowed up by the labyrinth, obliterated.

My little sister said with a slightly sad look, "Since they were too late in dealing with me...... the tens of thousands of people are already dead, Onii-chan."

"...... Will you, kill me too?"

She shook her head.

"Since I love you very much, Onii-chan, if it's now, I shall let you escape. But there's only about a minute left, I guess. I can only remain myself for one more minute. Farewell, Onii-chan."

The time limit was one minute.

"No. Let's escape together."

"Ah-haha, where to? The sickness is reproducing inside me. Forty more seconds."

Forty seconds.

"Saki!"

"Goodbye Onii-chan. I love you."

"I'll definitely save you......"

"Don't force yourself. I won't make it. I think I'm going to disappear......"

"No! I'll definitely save you!"

I stretched out my hand.

I desperately stretched out my hand.

I caught hold of her arm.

My little sister's eyes widened in surprise.

Both her color-changed eyes gleamed.

"Don't touch me! You'll...... you'll catch my sickness......"

"Shut up! That doesn't matter! I'm your big brother! I'm supposed to protect you! I'll definitely, save you......"

But at that moment, I could feel the sickness within my little sister invading my arm. My right arm suddenly felt heavy and languid.

"Stop!"

My little sister shouted in a shrill voice and brushed off my arm. I was sent flying. I landed headfirst and couldn't move because of the hard landing.

My little sister said with an anxious look, "...... Aah...... Aah, what should we do? You got infected with some of it. Some of the Apocalypse that's inside my head. But the time's already up. I can no longer remain myself. Bye bye, Onii-chan."

She waved. What was beneath her feet became infected by the sickness and rapidly became the labyrinth.

I cried out.

"Don't screw with me! I'll definitely...... I'll definitely save you!"

But into the darkness.

Into the labyrinth. My little sister disappeared.

And thus, I was the only one who survived.