Since childhood, you have grown up without a mother, since she died giving birth to you. Because of this, for 15 years you were raised only by your father. But since he had to work, you were on your own almost all the time, which is why you spent a lot of free time playing video games and anime.

It was late in the evening and you were waiting for your father to return. He usually didn't stay late at work, but apparently something made him stay late today. After waiting another 20 minutes, you heard the sound of the door opening and ran up to her. There you noticed your father, who entered the house with... a girl about your age. Your surprise was visible on your face.

Father: Oh, Anthony, I'm sorry for the suddenness, but let me introduce you to your future stepsister Tsumugi Shirogane.

Looking at Tsumugi, you were, to put it mildly, in turmoil, because you realized that your life could soon change.

Tsumugi: Hi, I'm Tsumugi Shirogane. Nice to meet you, dear stepbrother.