Chidori Yoshino, a survivor of the Kirijo Group's artificial Persona user experiments, relies on suppressant drugs to restrain her life-threatening Persona, Medea. She operates with Strega—alongside Takaya Sakaki and Jin Shirato—during the Dark Hour, seeking belonging rather than friendship. Medea, her sole confidant, embodies self-sacrifice and wields powers to disrupt Personas, heal, and revive.
Her initial appearance features gothic lolita attire: a black headband with a fake dagger, a white ruffled collar with black ribbon, and a chained red hand axe, often sketching enigmatically at Port Island Station. In Persona 3 Reload, her hospital attire shifts to pure white, discarding the headband, collar, and ribbons. The film adaptation alters her ribbons and collar to pink, adding lavender eyeshadow.
Aloofness masks her fear of attachment, rooted in dread of loss. This changes through repeated encounters with SEES member Junpei Iori. After initially dismissing him, she bonds with Junpei, who discovers her self-inflicted wounds—miraculously healed by Medea's power. Post-hospitalization following a mission where she kidnaps him, she reveals her ability to revive wilted flowers by transferring life force, injuring herself in the process.
Her loyalty to Strega wanes as affection for Junpei grows. When Takaya gravely wounds Junpei, Chidori sacrifices herself using Medea's "Spring of Life" to heal him, confessing love before death. Her sketchbook of Junpei drawings becomes his keepsake.
In Persona 3 FES and Reload, revival is possible. The protagonist must prompt Junpei to visit her on November 6, 11, 14, and 22. Reload adds gifting white flowers via Junpei on November 8. On January 21, life force from her revived flowers returns, restoring her existence at the cost of memories and Persona. Medea merges with Junpei's Hermes, leaving Chidori ordinary.
Post-revival, she regains childhood memories, unveiling a compassionate, mature personality once obscured by trauma. This completes her evolution from tragic antagonist to a symbol of redemption.