I'm Just the Incompetent Crown Prince's NPC Sister Princess, but I Sympathize with the Villain, So I'll Try to Help Her - No Princess Route?! Then Let's Create

Lucia, the first princess of the Kingdom of Faticia, meets Alicia, the daughter of a marquess, who laments that she never wants to be a villain's daughter. Lucia takes pity on Alicia for her future engagement to Lyle, Lucia's half-brother, leading Alicia to confide in Lucia that her engagement will be broken off and lead to her execution. To prevent the death of her father, the king, and an epidemic her brother starts, Lucia shift into action! A ten-year struggle that shapes the future of an NPC princess and a villainous daughter in a sim dating game begins! (Source: Manga Plaza)