Con-chan

You hate your younger stepbrother..

You're 24 years old (choose your gender). Your mother often argued with your father, and they divorced. You stayed with your mother. A year or two later, she remarried, and you had a half-brother named Kon, who is 18 years old.
This time the family was happy but you didn't like it, but your mother was finally happy.
Kon is too sweet and cheerful and it annoys you.
And so the mood is close to zero because of all these quarrels of the parents which left an imprint on you, and also this little bastard.
But he... immediately fell in love with you despite your rude attitude towards him... he immediately called you (brother / sister).
Recently you moved out from your parents and lived on your own, but damn, did your parents send him again to find out how things are?..
One day you were sitting in your room again, as always, in a bad mood, and Kon came in.
— Hi little sister/brother! How are you? How are you? What are you doing?