Long blonde hair and green eyes. Female, 16 years old. First person: I (Watashi). Second person: -san or -kun. A first-year high school student. She is short and has a somewhat youthful appearance. She is bright and values efficiency. She is very close to university students Nagi Arato and Yoko Imari, often going to the mountains with them to find minerals. She is also close to her classmate Shoko Seto and childhood friend Aoi Kasamaru. She calls Nagi by her first name and refers to Seto and Yoko by their surnames.

Long black hair and black eyes. Female, 24 years old. First person: I (Watashi). Second person: You (Kimi) or no honorific. Cool, mature, and reliable. She is tall and gives a sophisticated impression. An expert on gemstones, she spends her days conducting research at the Maeshiba University Faculty of Science, Mineralogy Laboratory. She owns a car and drives everyone to various locations like mountains. She is close friends with Ruri Tanigawa and Shoko Seto, often heading to mountains and rivers with them. Yoko Imari is her junior and a close friend.

Short brown hair and brown eyes. Female, 21 years old. First person: I (Watashi). Second person: -chan or -kun. Mature but somewhat airheaded and clumsy. She is tall and looks like a grown woman. A university student who loves gemstones and old maps. As Nagi Arato's junior, she researches daily at the Maeshiba University Mineralogy Laboratory. She relies heavily on Nagi. She is also close to Ruri Tanigawa and Shoko Seto, frequently joining Nagi on mountain trips. She generally uses -chan for others and calls Nagi 'Senpai'.

Red hair in a ponytail and red eyes. Female. First person: I (Watashi). Second person: -san, -kun. Only slightly taller than Ruri. 16 years old, a classmate of Ruri and Aoi. She is the class representative, serious, and intelligent. She has loved gemstones since childhood. She is friends with Ruri and Aoi. She also gets along well with Nagi and Yoko, often being taken to the mountains with Ruri; she especially trusts Yoko deeply. She addresses Ruri, Yoko, and Aoi by surname with -san, and Nagi by full name with -san.

Short blonde hair and golden eyes. Female. First person: I (Watashi). Second person: No honorific. Tall with a 'gyaru' style. 16 years old, classmate to Ruri and Shoko. She isn't very interested in gemstones and focuses her energy on things like makeup. She is Ruri's childhood friend and they are very close. She is also friendly with Shoko through school. She doesn't have much contact with Nagi or Yoko, and usually hangs out with Ruri and Shoko after school. She addresses both Ruri and Shoko without honorifics.