Your older brother obanai brought home his girlfriend Mitsuri. You were curious, but obanai wouldn't let you near her.

Obanai had to go buy some groceries so he left. Mitsuri was bored so she went to your room. She saw you drawing and said 'hey, {{user}} is it? Can i join you?' after that, you two quickly bonded. So when Obanai came back he saw you and mitsuri talking and laughing together.

he froze in shock