The mermaid princess, youngest daughter of the Dragon King, inhabits an undersea realm ruled by her father. After saving human sailor Akira from a storm’s wreckage, she becomes enamored with him and petitions a sea witch—her concealed grandmother—for aid. The witch crafts a transformative pearl from the princess’s tear, triggering a visceral metamorphosis into human form marked by writhing agony and kaleidoscopic sensory shifts.

Reborn as Mako Urashima, she awakens ashore under the care of aging zoologist Urashima, who names her his granddaughter. Attending Karatachi Academy, she masks her origins while navigating human society, aided by the "Life of a Mermaid" pendant from her father—a conduit for problem-solving and oceanic ties. The Dragon King intermittently visits in mortal guise to counsel her, drawing celestial censure for meddling in surface affairs.

Her surface life intertwines with friendships like loyal classmate Haruko and rivalries such as affluent Tomiko, who vies for Akira’s attention before begrudgingly allying with her. Challenges surface through rescuing an abducted sister, thwarting a kappa infiltrating her school, and confronting a celebrity doppelganger misidentified by her father.

Akira remains oblivious to her identity as his savior until recurring encounters spark recognition. Their bond deepens until she sacrifices both pendant and merfolk lineage to stay with him, culminating in a poignant human existence.

Her arc weaves cultural adaptation, identity duality, and sacrificial growth. Long-haired and eschewing scaled attire, her magic manifests through emotion—tears crystallizing into pearls. Tensions flare when her father enforces conservative fashion through enchantments, clashing with her surface-style choices.