I'm Just the Incompetent Crown Prince's NPC Sister Princess, but I Sympathize with the Villain, so I'll Try to Help Her

Lucia, the first princess of the Kingdom of Faticia, meets Alicia, the daughter of a marquis, who laments that she never wants to be a villainess. Alicia confides in Lucia that in the future, Alicia will be engaged to Lyle, Lucia's half-brother, but her engagement will be broken off which will lead to her execution. Feeling pity for Alicia, and in order to prevent the death of her father, the King, and to save her brother from becoming bedridden during the epidemic, Lucia shifts into action! A ten-year struggle that shapes the future of an NPC princess and a villainess in a dating sim begins!