Juju is an inflatable toy shaped like a dugong, purchased by Mika and her mother during a shopping trip aimed at helping Mika's father conquer his fear of the ocean. This ordinary object unexpectedly comes to life, becoming central to Mika's emotional journey.

Physically, Juju resembles a basic soft-vinyl flotation device with a simplistic dugong design, characterized by buoyancy and pliability. Initially purchased, he serves as Mika's companion in a backyard kiddie pool, filling the void of her father's absence after a postponed beach trip. Though inert at first, Juju later gains sentience and mobility, initiating conversation with Mika and proposing an alternative ocean adventure.

Juju exhibits a playful, encouraging, and protective personality. He demonstrates initiative by offering to transport Mika to the ocean himself when her father cannot. During their subsequent journey, Juju functions as both Mika's mount, carrying her on his back through the water, and her guide within a fantastical dream sequence. This sequence involves traveling to a magical island to confront "Mimika-sama," an antagonist holding Mika's father captive. Throughout this imagined rescue mission, Juju displays loyalty and support, participating in efforts to free Mika's father despite facing obstacles, including a monstrous entity.

His role extends beyond physical assistance, providing Mika emotional comfort during her disappointment. The dream adventure facilitated by Juju acts as a conduit for Mika to process her feelings about her father's fears and work commitments. Ultimately, Juju's presence and the shared experience within Mika's imagination contribute to her father confronting his own ocean-related trauma. Following the resolution of the father's fear and the realization of the actual beach trip, Juju reverts to his original state as an ordinary inflatable toy, used by the father as a flotation aid in the ocean alongside Mika.