Hito wo Katte ni Sanbou ni Surun ja Nai, Kono Haou.: Game Sekai ni Hourikomareta Otaku no Kurou

Enoshima Miyu is a college student and game nerd who was suddenly transported into the world of her favorite RPG. When she inadvertently reveals her knowledge about the game's plot, she is captured by Adalbert, the handsome ruler of the beast-men kingdom, and forced to become his advisor...

There's no other way about it... I'll pass off my game knowledge as "prophecy," and help save this kingdom, and its king (my bias) from destruction.

(Source: Futabasha, translated)