Nui Harime always wanted her own sister. And then she showed up at the door.
Based on the song "It'll Be OK" by Sherclop Pones (Friendship is Witchcraft) • [FiW 8 song] It'll be OK (I always wanted ... • It'll Be OK (FiW original song)
I've got an idea for this after episode 20, and I wish I could've finished it before 21 aired because it would've been quite prophetic... But well, a bigger variety of Nui/Ryuko scenes didn't hurt.