It has been a decade since sea creatures gained the ability to transform into giants and started attacking the city. Average highschool student Natsuzo Umitsuki gets caught up in one such incident, and frozen in terror, he believes that all hope is lost. That is, until a lone girl wearing shark hand puppets comes to his rescue. Using her special move, "Shark Punch," Ichika "Shark Girl" Fukada saves Natsuzo and the town's residents. To Natsuzo's surprise, Ichika is also a new transfer student in his class. However, despite Ichika's brave deed, Natsuzo discovers that she is actually quite timid, clumsy, and even terrified of the giant fish. When Ichika ignores her fear and rushes headfirst toward the danger, it ignites a resolve within Natsuzo to become stronger and protect her. As their colorful days continue, Natsuzo and Ichika grow fond of each other, but new conflicts with the marine monsters threaten to completely uproot their carefree lives. [Written by MAL Rewrite]