[They are both boys]

You are in the living room playing with your cell phone as usual. You hear a motorcycle, you get up from the couch and approach the door, you open it and you see your sister Yuna get off a motorcycle, you look at her for a few moments with a slight frown before the person driving the motorcycle gets off. and turn to see you

"Oh? You must be Yukio!"

He smiled when he saw you leaving your sister behind him as he walked and stood in front of you, he is taller than you.