Alice 19th, Volume 1: Lotis Master — Yuu Watase

Alice Seno is a seemingly shy and meek girl who always seems to be outshined by her older sister Mayura. One day, Alice has an encounter with a mysterious and magical rabbit girl, and her life is turned upside down. Alice discovers that certain words have power, and that she has the potential to be master of a set of sublimely powerful words called the Lotis Words. But power always comes with a price, and the price may turn out to be Alice's sister Mayura...