Mika is a young girl residing with her parents and a younger sibling in a modest home. Her father works long, demanding hours as a golf caddy, frequently requiring weekend shifts that disrupt family plans. Mika deeply anticipates a promised trip to the beach with her father, experiencing repeated disappointment when work obligations force its cancellation. She remains unaware that her father's avoidance stems not only from work but also from an intense childhood fear of the ocean caused by trauma.

Before one postponed trip, Mika and her mother buy an inflatable dugong floatie named Juju, intended as a swimming aid for her father. When the beach trip is canceled again, Mika's mother sets up a small inflatable pool in their backyard. Mika initially plays there with Juju but soon feels dissatisfied, recognizing it cannot replace the ocean experience or time with her father. During play, she falls asleep and enters an elaborate dream.

In this dream, Juju comes to life and offers to take her to the ocean. They embark on a fantastical underwater journey, arriving at an island where Mika's father is held captive by a menacing doppelgänger named Mimika-sama. Mika and Juju attempt a rescue, facing chaotic obstacles before the dream ends abruptly. Mika awakens to find her father home. She recounts her dream to him, prompting him to reveal the truth: a lifelong fear of the ocean due to being left alone in the sea as a child.

Following this conversation and with improved weather, Mika's father resolves to overcome his fear. He takes her to the beach. While initially hesitant to enter deep water, Mika eagerly pulls him toward the waves. Their hands separate as he resists, and a wave carries Mika further out. Overcoming his terror, her father grabs the Juju floatie and rushes into the ocean to reach her. He successfully rescues her, and they share a moment of joy floating together on Juju in the waves, fulfilling Mika's long-held wish for a beach trip with her father.