It takes a bit more on both fronts.

"I'm not sure... How can I know you're being honest with me, and the lamp's not just making you say what you think I want to hear?" Ruby asked Yang after several moments of consideration.

Yang pouted, before grinning mischievously. "Ah, don't be like that, Rubes," she said, floating closer as she lowered her arms, foregoing the use of Ruby's title for the sake of reassuring her. "I promise you, I'm being completely transparent," she added, gesturing towards her outfit. "Eh? Eh?"

Ruby groaned on reflex at the stupid pun. Classic Yang move, that. "Dang it Yang, how many times have I told you, your puns are... terrible..." she trailed off, staring at Yang in shock, her eyes welling up. "...it really is still you, mostly, isn't it? Only Big Sis would make a pun that bad!"

"Hey! Hurtful!" Yang protested, her submission being dialed back slightly as her genie and Yang aspects slowly found the equilibrium that suited her Mistress best. She'd still eagerly obey any command Ruby gave, but she was cooling it with the whole constantly doting bit.

Ruby laughed, and embraced Yang again. "I'm so glad you're okay!"

Yang embraced her back, grinning. "Mistress, I am much, much better than okay now, believe me."

They broke the hug, and Ruby stepped back, biting her lip and blushing as she held her hands behind her back and avoided eye contact, shifting apprehensively. Yang, still beaming eagerly, held her hands on her "hips." "So... You're a magic sex ****?" Ruby questioned, more to process than actually confirm.

"Uh huh!" Yang nodded. "And I really am hooked on it!"

"...ugh, this is so awkward!" Ruby tugged at her hair, going absolutely scarlet in the face. "For crying out loud, we're sisters!"

"And? I'm a consenting adult, and you would be one too if you made your move~!" Yang replied. "What's actually wrong with ****, inherently, anyway, once you subtract the whole "genetic deficiency" thing? Not like we could reproduce, we're both girls~! ...well, we could if I used my magic in some way or another, but if we did that, we could ensure the resulting offspring is perfectly healthy via the same means!"

"But it's... It's... Wait, what about the fact that it could be seen as exploitative?" Ruby asked Yang. "Like, an older sibling exploiting the trust a younger would be bad!" That wasn't even getting into so many other potential examples.

"Well, that's just another reason to make it taboo on a societal level," Yang shrugged. "But on a personal one, between us? Where's the exploitation? ...other than the fact that I would love for you to exploit me being your genie ****, but that's unrelated to us being related! So again, where is the harm in this case? I'm all ears, Mistress."

"Argh! I don't even know at this point!" Ruby whined, flustered and wrestling between her attraction to her sister, and her sense of propriety. She took a good look at Yang, and attraction won out. Fuck it, she was already accepting the idea that Yang was perfectly content as a sex ****, what was one more boundary? Especially given Yang's good points.