Following his parents' separation, Shima Kawauchi found consolation in the company of his loving grandfather. However, upon his grandfather's passing, Shima was plunged into a state of desolation and loneliness. One evening, while mourning by the seashore, Shima experienced a mishap that caused him to fall into the water. Struggling to stay afloat and overwhelmed by emotion, Shima was saved by an exceptionally attractive merman dubbed Isaki. Noticing the extent of Shima's anguish, Isaki insisted on accompanying him back home to ensure that he fully recuperated. As they adjusted to cohabiting, an intense connection burgeoned between them, surpassing both their divergent species and their sexual disparities.