Echo Girl, whose real name is Kyungju Choi, is a significant side character and arguably the antagonist in Zen's route in the game Mystic Messenger.
She is portrayed as a young, flirty idol who is a fan of Zen and persistently attempts to flirt with him. Her actions frequently cause problems and jealousy for the protagonist (MC) throughout Zen's storyline. Her character is primarily revealed through visual novel mode events and phone calls.
In essence, Echo Girl is a complication in Zen's route, adding conflict and drama to the storyline.
