Lost to Darkness (Kirito X Reader)
FYI: (g/n) means game name.
(g/n) was trapped inside the game Sword Art Online and was struggling to survive.
She accidentally killed a girl, believing she was her target. This girl happened to be Asuna, and she was traveling with the Black Swordsman, Kirito.
(g/n) has admired Kirito from the sidelines, knowing she could never beat him, yet she killed the girl he'd loved.
(g/n) managed to calm Kirito, and became one of his closest friends.