Decades passed. True to my oath that night, I never blinked, following the traces of their lives.

New humans from the south expanded their territory northward with incredible adaptability. The descendants of the families I protected gradually merged into that great flow. Some joined hands with the new humans, blurring the boundaries of their species by mixing blood; others travelled further in search of new lands.

“…According to calculation. Individuals fade, but information blends, rewritten into a more robust survival strategy.”

Whenever I watched them depart, a strange void grew within me. It wasn’t a theoretical resignation, but a lingering conflict similar to when I lost my old comrades. They survived by becoming ‘new’. But would that clumsy heat from the campfire that night be diluted and erased by the waves of efficient civilisation? With that anxiety, I continued to watch over the last person who remained in this land.

Finally, the infant who had been crying on that snowy night—the last one to stay—was facing his natural end.

Now a white-haired old man, he sat before the great rock as if aware his time had come. There, the drawing of a fish made with charcoal by the boy he once called brother remained vivid. The transparent protection I had applied continued to repel storms, snow, and the ruthless flow of time.

The old man traced the drawing with trembling fingertips.

“…Ah, it’s still… here. The light… my brothers saw…”

In his clouded eyes, reflecting the unfading record, dwelt the memories of life passed down by his ancestors. What I had once dismissed as a pointless doodle had become the sole sacred relic proving their existence.

I stopped hiding. In the form of a girl draped in pale blue light, I descended before him.

I asked myself: What is this form? Is it merely data efficiently mimicking the daughters of humans I once observed in Eden? Or is it something formed from the wordless ‘something’ that sprouted within me while spending time with them?

“…Do I look strange?”

When the old man’s eyes caught mine and narrowed into an incredibly gentle smile, I knew. This form was no longer a disguise. It was the ‘self’ my inner being had chosen as a result of touching their heat and sharing their pain.

“Well done. …My small, precious family.”

At my words, he smiled with satisfaction and quietly lowered his hands. I watched until the very last grain, as his final heartbeat stopped and his life returned to the planet’s cycle.

Several more centuries passed. The once-coastal line had been developed by the new humans and was now part of a highly advanced civilisation.

One day, young researchers on a geological survey found a strange rock in the shadow of a weathered cliff. While the surrounding rocks were heavily eroded, that spot alone remained as if time had stopped, preserving a vivid charcoal drawing.

“…Look at this. It’s over several thousand years old. How is it so perfectly preserved?” “It’s as if someone has been protecting it all this time.”

They were astonished, recording this unnaturally preserved primitive memory as a miracle of history.

High above, slipping through the eyes of the galactic surveillance net, a girl looked down from a break in the clouds. Within her chest, the clumsy, inefficient, yet warmer-than-anything memories she had received were engraved as eternal data that would not fade until the galaxy itself perished.

In a corner of the great story of human evolution, she alone knew that there was a hidden Eden that no one else knew, but would never be forgotten.