Eikoku Monogatari Shunka torikae Shou

The twin siblings Sei Shunran and Sei Shunrai are often mistaken for being of the opposite sex. Shunran, the older sister, is known for her intelligence, while Shunrai, her younger brother, possesses stunning beauty. Instead of entering the inner palace, Shunran plans to take the civil service test. To achieve this, the twins switch roles, with Shunran taking Shunrai's place in the palace, and Shunrai replacing her to sit the exam.