Tetora

Tetra is one of the players trapped in the MMORPG Elder Tale. She is actually male, but used a female Cleric character at the time of the Apocalypse. She is a self-proclaimed "Galaxy Idol," and has Equipment to fit the part, but is rather bad at singing herself.

Gold of the Kunie arc
A former resident of Minami and member of Light Indigo, she was sent by Kazuhiko to aid Shiroe at Susukino. Upon the completion of the mission, she asks Shiroe if she could join Log Horizon of her own free will, and was accepted. Tetra is actually a boy but due to the Apocalypse, became trapped within his female avatar. Shiroe was informed of this fact by Kazuhiko, but Naotsugu is still unaware of it. For kicks, Tetra often teases and flirts with Naotsugu.

Trivia

 * Tetra is one of the two known players to be trapped in an avatar of the opposite gender.  The other player, Akatsuki, managed to change her character gender to match her real life gender after acquiring a rare potion from Shiroe.