Hiroshi Ichikawa is a human orphan residing with his older sister Utako in the two-story Japanese apartment building, Arama-sō. Utako cares for her younger brother in the absence of their parents, and this apartment forms the primary setting for many of Hiroshi's interactions.

He forges a friendship with the protagonist after the latter arrives in the human world. Despite initial reservations, Hiroshi warms to non-human companions like Dracula, Wolfman, and Franken, who are part of the main group. His attire consistently features a yellow hat marked with an "H," a teal shirt, navy blue jeans, and light shoes.

In the 1981 film "Kaibutsu-kun: Invitation to Monster Land," Hiroshi journeys with the protagonist to Monster Land upon hearing news of the protagonist's father's illness. During this visit, Hiroshi is petrified after looking directly at the king of Monster Land, sparking a central conflict requiring intervention to reverse his condition.

The live-action film adaptation introduces a parallel storyline within the "Kingdom of Curry," featuring counterparts to Hiroshi and Utako named Ka and Princess Pirari. These characters resemble Hiroshi and Utako but exist within a distinct cultural and narrative context separate from the original human realm. Only Hiroshi's counterpart, Ka, appears in this alternate realm.