In the near future, much of the world has been forgotten at the bottom of the ocean due to rising sea levels. Natsuki Ikaruga, who lives in a small town surrounded and stranded by the sea, is invited by a mysterious woman, Catherine, to search for a treasure in his grandmother's house who was a marine geologist. One day, he dives to the bottom of the ocean in a submarine and encounters a mysterious capsule with a girl sleeping inside. The girl was a humanoid so sophisticated that she could be mistaken for a human.
I can't believe I've lost 
something so important,
،لا أصدِّق بأنّني فقدتُ شيئاً بهذه الأهمّية
Wie konnte ich nur
so etwas Wichtiges verlieren?
¿Cómo pude perder
algo tan importante?
¿Cómo he podido perder
algo tan importante?
Comment ai-je pu oublier
cet ordre ?
Ho perduto una cosa così importante...
Não acredito que perdi
um dado tão importante,
Как же я, такая продвинутая,
могла забыть столь важную информацию?