The main character, Kotaro Sakamoto, who was a Kamikaze pilot and was scattered to the sea, is washed ashore in present-day Okinawa, transcending time and space, and meets the other main character, Masaya Nakahara. A naked young man washes ashore on the coast of Okinawa. Mr. and Mrs. Miyazato welcome him home, name him "Umi" (from the sea), and care for him. Ummi loses his memory and stays at home in place of their son "Kaito" who committed suicide. One summer day, Masaya Nakahara, a friend of Kaito's who died at university in Tokyo, comes to offer incense.

Soon, Umi remembers that he is a past Kamikaze pilot [Kotaro Sakamoto] and decides to go to Tokyo. In Tokyo, Masaya takes Kotaro home and introduces him to his mother. And when he looked at his grandfather's belongings, he found a postcard from Junichi Kitajima. Kitajima was a member of the suicide squadron, just like Kotaro <Umi>. The next day, Masaya took Kotaro to the broadcasting station where his brother was. There, he heard a story about the Great East Japan Earthquake and was moved. He hears a speech by a political group on the street and discovers a new mission. Later, he meets with Kitajima again and talks about the war. Kotaro <Umi> laughs with satisfaction and hugs Masaya, saying, "Take care of Japan. He then heads for Yasukuni Shrine, where he disappears along with the members of the Hiryu Koubutai. Finally, at the seaside, Mr. and Mrs. Miyazato stare out at the sea and mutter, "Umi has become Wadatsumi. There is a young man walking to the seaside; is it Kotaro or his son Kaito...?