Oshi no Ichizu Sugiru Shuuchaku o, Watashi wa Mada Shiranai

Seha lives for Alexandrite, her favorite character in a dating sim game. When she learns he dies in other routes, the shock sends her into the game itself as Lady Arianell, a minor side character. Determined to save him, she decides to play the villain and force his romance with the heroine. Her plan seems simple until Alexandrite falls for her instead, his flirtatious brother also takes an interest, and the story veers wildly off-script. Can she save her fave without becoming his downfall?