I still don't understand how the blue outline works if the enemy Yoru uses his ultimate. Does it appear only when he's looking at you (if yes, from any distance?) or if he's close at a certain range?

I just looked at my friends list and this player is my friend even though i dont think ive played with them , they have an extremely high level, a weird status and have only 1 number as their tag, if anyone has any idea how they did this or...