Haruka had promised her that they would never be apart, that he would always come back to her.
But Haruka grew old, and suddenly, he wasn't able to go see his love as often as he used to. Once a day turned into once a week, once a week turned into once a month. Eventually his health gots so poor that he was not allowed to go to the sea, or even a nearby pool, anymore.
All he could do was to sit in his bed everyday, longingly looking out the window.
But he promised that he would visit again, he gave her his word that they would meet again, she is waiting, he knows she is waiting.
But he never came back.