Louise is a noble lady who loves books and magic devices. One day, she suddenly had her fiancé 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.

“What do you think about this?”
(No... I couldn't possibly tell him about that.)

On the other hand, Louise’s potential as a researcher is also starting to bloom...?

Louise, a noble lady who loves reading and researching magic tools, leads a double life pretending to be her twin sister. Suddenly one day, her fiancé breaks off their engagement and chooses to be with her sister instead. All seems lost to her when she also has to give up her dream of becoming a magic tool researcher, but a reunion with her first love, the first prince Lucius, saves her from her misery. As they spend time together reading books in the hidden archives and looking around at different magic tool shops, Louise slowly regains her confidence. On top of that, her heart flutters every time unconsciously sweet words leave the prince's mouth. The mood is perfect and it seems like it's seconds before they can finally be together, but the past she wants to keep hidden gets in the way.

"How...do you feel about me?"
(He asks, but... I can't do it. I can't tell him.)

Meanwhile, her potential as a researcher begins to blossom and leads to... A true love fantasy full of misunderstandings between a magic tool-obsessed noble lady and a stoic older prince awaits!