Lets start with a light mental domination and see where it leads.

Gotta focus. As much fun as all this is, you have a time limit on breaking your sister in and while she might not be as physically as capable as Fuckbunny over here, you have no doubts that mentally she is as strong, if not stronger. You have to fight your natural inclination to be lazy if you want to be able to keep your powers and NOT go back to being the loser you were yesterday.

You're a badass, yeah. You're a super powered boss-man of a multi million dollar luxury apartment complex and you fuck bitches like Alina all day, every day. You psych yourself up like only a dumbass would as you step into the steamy shower where Alina is. The water is hot. Almost uncomfortably hot. She seems almost zoned out. You note she's washing herself pretty aggressively, like she's trying to clean off something that won't come off... ever. Of course, being the shit-heel that you are, you figure she's getting herself all cleaned up so she'd be nice and fresh for you again.

You step in and take a moment to rinse yourself off while she eyes you warily, before grabbing her by her face and forcing her to her knees.

"Wash my dick for me. Fuckslut."

She holds eye contact with you as she reaches over to get some soap on her hands before lathering up your cock. She even reaches down into your undercarriage to get at your ass. Smart girl. Probably figures you'll make her tongue your asshole again and she wants to make sure it's clean beforehand.
Without another word, you pry her mouth open and take a big sniff. Minty.

"Good, you brushed your teeth already. I didn't really want to kiss you before you brushed seeing as you were eating my ass not 20 minutes ago. Good girl."

You can tell she wants to tell you to go fuck yourself, but she wisely holds her tongue. She probably doesn't want another facefucking session so soon.

Well, she thought wrong. You give her a minute or two to lather you up and rinse your cock, then look down at her expectantly.

"Are you sure it's clean?"
"Yes... sir."
"Double check."

Alina reaches for the soap again but you grab her hands and stop her.

"No, I mean check to make sure you rinsed it properly and didn't leave any soap scum. With your tongue."
"MMmmph."
"That's right, you little sucky sucky bitch. That's what your mouth is for."

You enjoy the sensation of the warm water splattering against your skin as Alina closes her eyes and opens her mouth. Her tongue feels almost cool against your glans compared to the hot water, you close your eyes and enjoy the moment. You are a king. You are HER king. You've watched enough porn over the course of your life to at least know what you need to say and do to fake it, even if you've never had a chance to actually put any of it to practice.

But looks like you're getting a crash course on being dominant, on an unfortunately VERY unwilling partner. Not that it matters to you.

"Go deeper, you useless bitch, you better be tongue bathing my balls."

Alina tries to deep throat your cock, but she's unable to hilt it in her throat like she was able to before.
... Wait.. did your cock get bigger? Huh?
You could have sworn you hilted your cock balls deep in her throat an hour ago, but now she's having trouble swallowing the whole thing. And you don't think it's for lack of trying on her part. You're pretty sure your cock managed to grow another inch or so in the past hour. You're pretty familiar with what it looks like, and it's DEFINITELY bigger.

Not to look a gift horse in the mouth, but what the fuck? I mean, you don't think you've EVER been this hard for a girl before, but that doesn't make your dick get magically bigger now, does it?