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.
Of course not. It's not like 
there's some shipwreck down here.
بالطّبع لا. ليس وكأنّه يوجد
حُطام سفينة في الأسفل هنا
Träum weiter.
Das hier ist kein Schiffswrack.
Claro que no.
Claro que no.
Rêve pas. J’explore pas l’épave
d’un navire naufragé.
Figurati se trovo qualcosa del genere!
É claro que não. Eu não tô
em um navio naufragado.
Ага, мечтайте.
มันจะไปมีได้ไงล่ะ