Mizuki Hase is a male human teenager and a close friend of the protagonist Yushi Inaba in Elegant Yokai Apartment Life. He first met Yushi in their third year of elementary school, and their friendship continued into middle school and high school. Hase is tall with black hair and brown eyes, and he is generally described as having a cool and calm demeanor. He comes from a wealthy family and has a strong ambition to become an elite businessman, driven by a desire to surpass his father and his sister in professional achievement.

Initially, Hase is unaware that Yushi lives in the Kotobuki-so apartments among ghosts, yokai, and other supernatural beings. His discovery of this hidden world occurs during a fight with a gang, when Yushi is forced to summon creatures from the Petit Hierozoicon. After witnessing this, Hase becomes a regular visitor to the supernatural apartment building. He develops a close bond with the ghost boy Kuri and the ghost dog Shiro, often sharing a futon with Kuri when he stays overnight at Yushi’s room. He also shows generosity toward the other residents, frequently bringing gifts and food as a gesture of gratitude for the care they provide to Yushi.

Hase’s role in the story is that of Yushi’s best friend and a link to Yushi’s life outside the supernatural community. He maintains a sense of normalcy and grounded ambition, pursuing his goal of succeeding in the business world while also embracing the strange and warm environment of Kotobuki-so. His development involves gradually accepting the supernatural world and integrating it with his own life, all while supporting Yushi through various challenges. Notable abilities are not a focus for Hase, as he remains a purely human character with no magical or exorcist powers, but his loyalty, level-headedness, and material generosity are key traits that define his role in the series.