Koushaku Reijou Theresia no Fukushuu: Akuma no Chikara, Okarishimasu

公爵令嬢ティアレシアの復讐　～悪魔の力、お借りします～ · The Duke’s Daughter Tiaresia Takes Revenge · The Revenge of the Duke’s Daughter Theresia: I’ll Borrow the Power of the Demon

Koushaku Reijou Theresia no Fukushuu: Akuma no Chikara, Okarishimasu is a completed Demons, Reincarnation manga (2020). Read it online free on XOmanga.

Queen Kristian was framed by her half-sister and executed at just 16 years old. Another sixteen years have passed since then, and the daughter of a duke is about to make her societal debut—her name is Tiaresia. Always close at hand is her loyal servant, growing more impatient by the day. In truth, this handsome servant is a demon, waiting to reap the rewards of a magical contract made with Tiaresia—the reincarnated former queen Kristian. Together, they plan to exact a calculated and tragic revenge. (Source: Manga UP! Global)