Her sister

Luna realized that she went too far when she saw her sister ignoring her and being disappointed by what she said .

Her sister's relationship with Kris was always blurry to her .In the original plot he was her right hand .He cherished her as a leader and followed her path, and in the end he died protecting her .

That was totally expected from him but his actions were too invested in her sister's life .He was a hero to Isa in the past but that changed when she left the clan .

Now, when she thinks about it with patience she thinks that he might have been in love with Sira. But her sister never gave him a chance to talk to her in that way .And after all those years she just chose a random person to fall in love with .

And that person happened to be the villain that executed her later .

Even Sira treated him like shit despite his loyalty. 

In the afternoon, when Luna was playing around with her phone she heard the doorbell, seconds later her sister showed up to open it .