At 16, Mamori Tokonome faces ridicule at school due to her surname's embarrassing connotations. But her challenges escalate when she gets kidnapped during gym class and lands on Mermaid Island. There, she partners with the mysterious Mirei Shikishima, who unlocks Mamori's combat transformation abilities with a kiss. Together, they navigate the island's dangers, encountering allies like Charlotte, the ruthless Exter leader, and foes like Meifon and Akira Hiiragi. Survival hinges on their intimate bond amidst a backdrop of scandal and intrigue.