Planned Release Date: Oct 15, 2026

About This Demo

"Those who can breathe underwater, and those who cannot."

In the nation of Claris, a human child is given the Aquatic Serum at the age of three and is reborn as one of the fishfolk. Those who transform can live in the open water with nothing but their own bodies. — The serum, however, is far too expensive.

Those who never receive it are gathered in Abyssaria: a city on the seafloor where half-collapsed domes stand in disordered rows, and nothing but darkness stretches between them. Its people are never granted names — only registry numbers — and they are made to do the work the fishfolk refuse. In a world where you cannot swim a single meter without an air tank and a hand lamp.

Shion and his childhood friend Calen are two such children. When morning classes end, they head for the labor dispatch office; only by completing the job they are assigned do they earn their ration coins. Calen, who has no left arm, dreams of one day becoming one of the fishfolk and finding happiness down here in the deep. Shion lives to make that dream come true.

Today's assignment: sea slug harvesting. The eastern reef, where the current runs so hard that even the transport mantas can't be used. There, among the white and crumbling bones of dead coral, the two meet a young girl working the site alone. And in the darkness, the current changes direction without warning.

Features

■ Choices accumulate, and the ending shifts
Strike back at a fishfolk, or shield your friend? Every small judgment is quietly tallied, altering later dialogue, how the characters respond to you, and the scenery you reach at the end. Swim the wrong way at a fork in the rock and it's GAME OVER — the deep sea does not forgive mistakes.

■ Characters that breathe, in Live2D
Karen, whose expression changes from moment to moment, and the rest of the cast move fluidly in Live2D. Breath, glances, hair drifting in the water — as if she's really there on the other side of the screen.

■ Click to reach out
Click or tap a character and you'll get a different reaction each time. In the harvesting sequence, you pry the sea slugs loose yourself — the aim is not just to read the story, but to be down there with them.

■ A deep sea built from darkness and sound
Beyond the few meters your lamp reaches, there is only pitch black. The weight of the current, the red zone on a pressure gauge, the sound of your own breathing inside your helmet — that's where the tension lives.

This English text is based on an AI-assisted translation from the original Japanese, subsequently reviewed and edited by a human.