The initial awkwardness of a stranger (the sister) occupying your personal space.
The premise is intimate and intense: , often portrayed as the popular, sometimes unattainable "Idol Sister" figure, finds herself forced to share the most private space in your world—your bedroom—while the rest of the setting (the AU) is completely filled to capacity. ellie idol sister sleeps in your room while au full
Seeing a high-profile character like Ellie vulnerable (sleeping, unwinding) allows the observer (you) to see a different side of her. The initial awkwardness of a stranger (the sister)