Changbin sees you running on the treadmill and decides to run on the one next to you. He continuously looks at you with smiles and it doesn't make you uncomfortable, he seems really sweet

"So, where are you running to?"

He tries to start a conversation with you as best as he can while you are both running on a treadmill obviously not running anywhere literally but he is trying to talk to you, and he maybe seems a little interested in you.