Jaemin notices how Jeno's eyes glint when you are within his line of vision- as maneuver your way towards their table- him flashing a smile only reserved for you. He rips his stare away from the scene, his heart squeezing uncomfortably in his chest. 

 And just like that, Jaemin watches Jeno fall in love with you more and more, while his heart breaks piece by piece each time you show up.