@shafiq95
As far I remember in the fireworks festival it was confirmed that she has a weak heart so that means she can die right ?
Also I think in the last chapter her sister said to give up on her cuz she is different which means she is weak I think
@Wickedhero
Her doctor cleared to be completely healthy post operation.
Isaki's fear came from this idea that, because her heart runs "differently" than normal, there COULD still be a chance that something might go wrong for her, per her own point of view.