Mitame Youjo na Akuyaku Reijou wa, Koori no Koutaishi (Tokidoki Kawaii) no Ude no Naka.

To secure the future of her kingdom, Juliana, the daughter of a duke, accepts an arranged engagement to Folkhart, the notoriously cold and ruthless Crown Prince of a neighboring empire. To navigate this dangerous alliance, she employs magic to physically de-age herself, adopting the disguise of a four-year-old child known as Princess Liane. Her situation grows far more complicated when Enzo, a valet who claims to have arrived from another world, reveals a shocking truth: their reality is actually an otome game, and Juliana is destined to be its villainess, fated for absolute ruin. Armed with this terrifying knowledge, Juliana realizes that if the merciless Folkhart ever discovers her true identity or her deceptive methods, the consequences will extend far beyond her own demise—her entire nation could be wiped out alongside her. Despite the overwhelming odds stacked against her, she refuses to accept her scripted doom. With unyielding determination, she resolves to fight against her fate, declaring that she will never give up as she navigates the treacherous path ahead in her youthful guise.