‎Nagisa Miois an oceanologist at the University of Marine Science and Technology of Shibaur. She is crazy about the depths of the sea and the inhabitants living there. But despite the cheerful smile and a kind soft character, the girl does not like to talk about her family and the past.

‎Hasuda Rintaro is the second son of a rich family who is feared by others because they believe that he "should not be approached". But in fact he is a timid young man with a "pure heart and an open soul."

Rintaro returned to Japan due to his father's poor health and led a sea resort development project promoted by their family firm. Mio wants to protect the ocean and against the development of resorts, and Rintaro in turn wants to implement it, "even at the cost of his own life." ‎‎But when Mio and Rintaro meet because of the project, they fall in love. ‎‎However, their love is forbidden, because Mio has a secret that can shock everyone ...‎