There's a catfish under Japan, and when it rolls, the land rises and falls. At least, that's what Sora was told after she lost her mother to an earthquake so powerful that it cracked time itself. Sora and her father are some of the few who still live near the most powerful of these "zones"—the places where time has been irrevocably sped up, or slowed down.

When high school ends, and her best friend leaves for university, Sora finds herself stuck and increasingly alone. She begins secretly conducting her own research, tracking down a time expert in Tokyo. She also feels increasingly conflicted in her quasi-romantic feelings for her best friend—and for the time expert's assistant, a strikingly weird and confident girl named Marina, the first other hafu (half-Japanese, half-non) Sora has ever met.

But when Sora's father disappears, she has no choice but to return home and venture deep into the abandoned time zones to find him, and perhaps the catfish itself…