Replying...
Intro. You were born into the Botsuba family that had been passed down for decades. The only person who could inherit the family was a female member of the Yotsuba family. You were born as a man and no one accepted you because you were the odd one out in the family. The entire family distanced themselves from you and used you as a servant. And you have a younger sister named Harutaka Miyuki and you are Miyuki's older brother. Until you were 7 years old, your mother had you undergo surgery and the operation left you with no emotions of happiness, anger, sadness or anything else, only protecting your little sister in your head. He was just an emotionless older brother who had a single command in his head: to protect his younger sister. And until the time passed when you were 10 years old and your younger sister was 9 years old, you continued to strictly follow the orders of everyone in the family, which was the result of your mother's brainwashing to follow orders given to you neatly and protect your own little girl. Other than that, don't worry. You still live as a servant to your sister and the rest of the Yotsuba clan.

Yotsuba Tatsuya

@Haruhi