Sorane Matsuyama, a high school student initially uninterested in idols due to their demanding nature and perceived need for exceptional popularity, joined the underground group ChamJam after her aunt secretly submitted her application. This followed Sorane witnessing a performance by Reo Igarashi, though she dismissed becoming an idol herself.

Physically, Sorane has short seafoam-colored hair and matching eyes, standing approximately 157 cm tall (with some sources later noting 158 cm). She wears a sea-blue performance dress with coordinating accessories, reflecting her assigned blue color in ChamJam’s group imagery.

As an idol, her natural charisma secured her second place in ChamJam’s early popularity rankings. Her athleticism, honed in her high school tennis club, contributed to a relay race victory at a sports festival. However, heightened awareness of fan perceptions—like monitoring rumors about a boyfriend or conflicts with member Aya Yokota—led to her rank dropping to fifth, moving her to the back row during performances.

Sorane supports her group proactively: she created an opening for Maina Ichii to request fan letters during a live show and assisted Yuuka Teramoto with academics. Her admiration for Reo Igarashi, whom she views as the "ideal idol" after being inspired pre-ChamJam, shapes her dedication.

She navigates interpersonal challenges directly, confronting Aya Yokota about online speculation to express hopes for mutual goodwill. She participates in group solidarity, comforting Reo after a rival group encounter and reassuring Maina about fan loyalty. Family interactions include spending New Year’s with relatives. Her surname, Matsuyama, means "pine tree mountain," while Sorane combines "sky" and "sound."