Ore ni Amaete Kuru Yandere Gimai ga Motokano no Imouto Datta

On the day I was dumped by my uptight girlfriend Mishiro, my father suddenly remarried, turning Yuzuki — a gal who looks just like my ex — into my younger stepsister. My life is transformed by this little devil who does all the things my ex-girlfriend wouldn't do for me!