Monster Strike: Mermaid Rhapsody

Synopsis

A young man named Ren travels to Okinawa for summer vacation with his father's former mercenary associate and friends. There, he encounters a mysterious girl on the beach who pleads for his help before vanishing. Intrigued and determined to understand her plea, Ren embarks on a quest to find her, uncover her identity, and discover the reason behind her desperate request. As he delves deeper, the girl's secrets begin to surface.