Lin's friend, Airi, is being stalked. The three brothers immediately come to her aid, saying they'll take care of the stalker. They sneakily follow Airi around and soon find out it's not just a stalker that follows Airi around...
didn't know that, which means 
you are unmistakably a stalker!
ni siquiera lo sabía, 
así que eso te hace el acosador.
ni siquiera lo sabía, así que eso te convierte en el acosador.
sabia disso, então você só pode ser um stalker!