To the Cradle in the Ocean

S1 E1: In the near future, much of the world has been forgotten at the bottom of the ocean. Natsuki Ikaruga is invited by a mysterious woman to search for a treasure in his grandmother's house. 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.