Based on the Fire Emblem Games. Note: Released in Enix Supercomic Gekijoh Volume 2.

Claire was treated as a failed princess because she didn't follow the education of a proper lady. She was sent on an arranged marriage with an enemy kingdom, expecting to lose her life at any moment. Instead, she was welcomed with open arms and unexpectedly made the fiance of the crown prince. In fact, she had been eagerly awaited as a "living fount of knowledge." She had been treated as a useless person in her homeland, but now she could embark on domestic reforms and started making paper to help her new home. However, some people did not take kindly to this...... Claire tried stop her own poisoning and get out of the situation, but... (Source: Earthstar Luna, translated)

Haruichi, a mysterious boy who can see people's true nature through colors, meets Sayuri, a girl who belongs to the organisation "Kisaragi," which observes youkai escaped to the human realm.