Five years past, enigmatic bubbles that defied gravity fell from the sky over Earth. Following a massive blast of unknown cause, Tokyo became the epicenter, its streets sealed inside a colossal bubble. This event, dubbed the "Bubble Fall," sank the former capital into a gravity‑distorting ocean; authorities marked it as forbidden, and its inhabitants fled.
Now, the children left homeless by the Bubble Fall illegally occupy Tokyo"s ruins, engaging in perilous parkour squad contests across its crumbling structures. Hibiki—a gifted prodigy who can leap between bubbles—asserts he hears echoes from the Tokyo Tower. Driven to solve its riddles, he heads toward the source but plunges into the submerged depths.
A mysterious girl, whom he later calls Uta, rescues him. Yet Hibiki remains unaware that Uta"s presence will unveil the truth behind the calamity that reshaped their world.
