Iwa leads three supernatural entities assigned to watch over the protagonist after her father's death. These beings form from sky droplets, manifesting as yokai upon reaching the island. Iwa possesses a large, sumo-like build, a prominent square jaw, perpetually visible gold teeth, and a beard—features that could seem intimidating but clash with his generally clumsy, earnest nature. His bug-eyed look contributes to a distinct visual design drawing partial inspiration from Edo-period supernatural art, though his appearance is original.

Characterized by honesty and occasional social awkwardness, Iwa acts paternally within his group, showing particular protectiveness toward the smallest member, Mame. Despite being the leader, he frequently causes comedic mishaps and proves gullible. His dialogue features dry humor, like commenting on another character's "amphibian look." Initially motivated by self-interest, such as stealing food and causing trouble for humans, Iwa gradually develops genuine concern for the protagonist. This evolution culminates when he prioritizes her urgent needs over supernatural regulations, defying rules to assist during a critical medical emergency.

Narratively, Iwa provides comic relief through physical humor and acts as an emotional catalyst. His group's chaotic actions—orchard raids and property damage like breaking a significant mirror—create conflicts that inadvertently push the protagonist toward community interaction and growth. His presence connects to themes exploring links between ancestral spirits and the living, positioning these yokai as temporary guardians until the father completes his transition to the afterlife. During a climactic typhoon, Iwa coordinates with numerous other spirits to overcome obstacles, demonstrating his capacity for cooperative leadership when serious action is required. This moment underscores his shift from mischievous instigator to committed protector fulfilling his guardianship purpose.