Mushikaburi-hime

Mushikaburi-hime summary: Although only the fiancée of the Crown Prince, Christopher, in name, Eliana, is a noble lady that enjoys her life by reading books all day. One fateful day, Eliana ended up knowing that there was a noble lady that apparently the prince was all affectionate with. Instantly, she thought that a girl that actually loved the prince appeared!! And, while thinking about that, Eliana started to prepare for the approaching time of when her engagement would be cancelled... (Source: Ichijinsha, translated)