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.
There was a sudden sea rise that 
happened across the globe.
كان هناك ارتفاع مفاجئ في منسوب
البحر حصل في أنحاء المعمورة
Der Meeresspiegel war weltweit
schlagartig angestiegen.
El nivel del mar aumentó
radicalmente por todo el mundo.
El nivel del mar aumentó
radicalmente por todo el mundo.
Une élévation fulgurante
du niveau de la mer
C'è stato un innalzamento dei mari
su scala globale.
O nível do mar subiu repentinamente
por todo o planeta.
Когда по всему миру резко
поднялся уровень воды,