Yousuke jumps in surprise himself when he hears the crashing.

"Souji! Just-- hang on!"

He drops his bag of food on the floor and runs to where he remembers his room being. He feels about in the dark, and his socks slip a bit on the wooden stairs and he stumbles, but he has a railing to steady himself with. So we don't end up with a double nosebleed situation. When he gets to the top, he finds Souji's doorway with his hands and slides them around the threshold until his hand runs over the light switch, and he flips it on.

His eyes survey the room in a split second, and his mind can't process what he sees. He doesn't have the capacity. In a minute he'd have the time to figure it out.

Instead, he focuses on Souji, and forgets about everything else.

"Dude," he breathes, and gets down to his knees. He sees the blood, and there's more than worry in his voice "are you okay? I mean, your face..."

Yousuke knows that there's more wrong than just his nosebleed, but we're starting with the basics.