Sennou Shitsuji

When the daughter of the Takato family, Ichigo, returns from studying in the UK after a year, she notices a strange situation in her family. Apparently, they all seem to have been brainwashed by the butler, Seijuurou Kuki, who came while Ichigo was abroad. And so begins her efforts to return her family back to normal while desperately resisting Kuki's influence.

(Source: Comic Natalie, translated)