Herscherik

The life of Ryouko Hayakawa, a hard-core otaku, came to an abrupt end the day before her 35th birthday, before she was reincarnated as a beautiful prince in a fantasy world. However, her dream-like royal life didn't last long, as she soon uncovered the depths of politics and corruption of her kingdom. To protect the king and his people, Ryouko, reincarnated as Prince Herscherik, resolved to conquer the darkness within his country. The problem was, the prince had no physical strength or magical powers, and even his stunning looks were surpassed by every other member of the royal family. Still, the prince persevered, using the skills he acquired during his previous life—the experience of an office worker, Ryouko's drive for change, and her otaku brain.

(Source: J-Novel Club)