Hiroshi Ichikawa, an orphan, lives with his older sister Utako Ichikawa in the modest two-story apartment complex Arama-sō. Utako acts as his caregiver following their parents' loss, establishing their sibling relationship as a core element of his background. Hiroshi possesses black hair and black eyes. His signature attire includes a yellow hat marked with an "H", a teal shirt, navy blue jeans, and light shoes, creating a consistent visual identity.

Functioning as the deuteragonist, Hiroshi serves as the central protagonist's primary human friend and connection. He regularly interacts with supernatural beings visiting the human world, placing him at the crossroads of ordinary life and extraordinary monster encounters. His daily routine involves attending school with classmates Ako, Kizao, and Banno, though these peers are absent from later adaptations.

The live-action television drama adaptation retains Hiroshi's core relationship with Utako and their home at Arama-sō. This version, starring actor Tatsuomi Hamada as Hiroshi, introduces new characters like a landlady and a policeman. The plot follows Hiroshi and Utako befriending a prince during his ascetic training in the human world, confronting threats from demonic groups together.

In the subsequent live-action film, Hiroshi's character remains consistent, but the narrative incorporates a parallel universe element. Transported to the "Kingdom of Curry," Hiroshi and Utako have royal counterparts named Ka and Princess Pirari. These counterparts physically resemble them but exist within a distinct cultural context, exploring variations on the characters' core identities without altering Hiroshi's fundamental human background.

Across all versions, Hiroshi's narrative role centers on providing an ordinary human perspective amidst fantastical events, maintaining his vital sibling bond with Utako, and anchoring the audience through relatable experiences while supporting the protagonist's journey.