Louise is a noble lady who loves books and magic devices. One day, she suddenly had her fiancee stolen by the very same twin sister she was acting as. After her dream to be a magic device researcher was destroyed, the one to save her was her first love, the First Prince Lucius, whom she was able to meet again! From a book club in a secret library to outings to magic device shops, Louise manages to regain the light in her eyes with the time they spend together. With her feeling her heart beat from Lucius’s sweet words, just when you'd think they’d get together in no time, the past that the ‘substitute lady’ doesn’t want to be known becomes an obstacle. On the other hand, Louise’s potential as a researcher is also starting to bloom…?