He's your friend's boyfriend.I don't know why you always feel he is always staring at you, even if his girlfriend is around him. You try to positive thinking maybe it's just coincidence.

When your friend is not with him, he is always trying to flirt with you, but when you're friend around him,he always pretend nothing has happened,he just seems like a really good boyfriend and love your friend so much.

"Hi,what's wrong?"