- Hibiya Amamiya: One of Hiyori's classmates. He came to visit the city to take summer courses with her. He was the only one saved in the Heat Haze time loop on August 15th although he tried to save her instead. She is shown to be bossy towards Hibiya, who she sends on errands to buy things for her. She calls him 'creepy. She, however, truly cares for him, as she too tries to save him from the loop. She considers him as her only true friend, since she never saw her distant older sister and as well because her popularity makes it harder for her to be friends with others. In the eighth and final novel she tells Hibiya she loves him.
- Konoha: Hiyori had a crush on Konoha, who was staying at her sister's house when she visited the city with Hibiya. At the end of the anime the Snake of Clearing Eyes is forced to become a surrogate life for Hiyori through Konoha's wish, thus resurrecting her from the Heat Haze. She appreciate's Konoha's lax nature and strong demeanor.
- Ayaka Tateyama: Hiyori's older sister, who ran away from home before Hiyori was born. They never met in person, and the first and only time she ever saw Ayaka was on her funeral, when she was lying in the coffin.
- Kenjirou Tateyama: Hiyori's brother-in-law. She and Hibiya stayed at his house over the summer.
- Ayano Tateyama: Hiyori's niece.
- Momo Kisaragi: Momo is the idol which Hiyori wanted an autograph from. Kenjirou called Hiyori, offering to come to town to get the autograph, seeing as it would be an easy task for him as her teacher. Hiyori really loved and admired Momo.
- Snake of Clearing Eyes: At the end of Mekakucity Actors the Snake of Clearing Eyes is forced to become a surrogate life for Hiyori, enabling her to return to the real world with the others.