Leah woke up with a sense of sever discomfort. As much as she tried to ignore it and go back to sleep, eventually it got too painful to ignore. With a groan of annoyance, she opened her eyes and threw her covers off...to find she's naked save for a yellow diaper. She blinks rapidly at the sight, mind still waking up before she felt a pure sense of embarrassment and anger---no one else could've done this except for Tina. She quickly went to grab a t-shirt all while dancing in place, trying and failing to deal with a bizarre sense of pressure and discomfort. She marched out the room and banged on Tina's door.
"Tina, why was I naked?!" The teen shouted, dancing in place and sub consciously grabbing her crotch. Tina opens the door after a moment, looking quite disheveled herself.
"Leah, I- sorry, but last night I...needed...to..." Tina paused as she looked at the teen doing the most desperate of potty dances with an angry face, "Leah, do you need to go potty?"
"What? No, I-" She paused as she hadn't fully considered it. Realizing how little time there was, Tina grabbed Leah's hand and pulled her along.
"Follow me, quickly." And any resistance was gone as the girl obeyed without question. With the speed and grace of a hawk, Tina pulled Leah's diaper down and pushed her onto the toilet.
"Okay, now try to pee."
Leah was a little upset, angry that she was stripped in her sleep only to be stripped naked immediately after, but obeyed as she's been conditioned to do. The bathroom filled with the sound of liquid hitting liquid, and Leah letting out a shameless sigh of relief. The relief was short lived as she covered her chest and tried to cover her crotch.
"Hey, a bit of privacy Tina!"
Tina's half-awake mind only then noticed her fully nude stepdaughter, tempted to say 'There's not really anything to hide' if she didn't think it'd cause further hostility. She purposely turned her gaze to the other side of the bathroom.
"As I was saying, I needed to change you last night. It's why I made you wear the onesie, to make it easier. What I wasn't expecting was for you to poop so much that you popped the bottom open. I needed to undress you to properly change you. I guess I was so tired, I forgot to redress you. My bad."
Leah's anger immediately turned to shame and guilt; for all of Leah's sudden loss of continence, Tina at least was taking the initiative to make it less inconvenient for Leah.
"Ah, well I...guess I'm sorry for yelling. Sorry, all this diaper nonsense has put me on edge."
"And for good reason. But hey! You made it to the toilet! That's a good sign!"
Leah felt herself flush further; if Tina hadn't taken her here, she literally wouldn't have even realized she needed to pee. Heck, she's not suer she would've been able to take the diaper off or sat on the toilet properly. Why was potty training so hard? Or rather, hard for her?
"That's good, I guess."
"Come on Leah, cheer up! Keep doing this, and you'll be out of diapers in no time."
"If you say so."
Leah finally stopped peeing with one final sigh of relief. Leah shifting uncomfortably on top of it, unsure of what to do next. As she maneuvered herself to hop off, Tina turned with a gasp.
"No, Leah, first you have to wipe!"
"W-wipe?" Her mind blanked on what that even means. Wipe what? The answer felt slightly more obvious as she looked at her urine splattered crotch.
"Right. Here, let me show you." Tina turned around and grabbed a bit of toilet paper.
"W-wait, what!? No way, I can-"
"Leah, tell the truth, do you know how?"
Leah gapped before she squeaked out a tiny "No."
"Then let me show you."
As such, Leah watched as the woman wiped the excess urine off of her groin, feeling a little violated.
"There. After that, you press this little hand here to flush it away. Got it?" The woman explained patronizingly. Leah felt incredibly talked down to, but knew this was all new information. She pushed the plunger, and jumped a little from the resulting loud flush.
"It's fine. I know the loud sound is a little scary, but it's nothing to be afraid of."
Leah nodded, face redder than paint.
"Can I get dressed now?"
"Well, I need to put you in a new diaper first. Are you ready?"
Leah just groaned in response.
In short order, Leah was diapered and dressed in her new shorttails, waddling slightly as she gets used to the bulky underwear.
"God, it's so loud! Can't I wear anything less noisy?"
"I'm afraid not. You're a little too accident prone right now."
"I had, like, one accident yesterday!"
"Two, actually. And that's not including the ones the had at night."
Leah shut up after that, accepting that she was just going to have to deal with it. After they have a light breakfast, the two prepare to go to Leah's new school for the foreseeable future. Unfortunately for Leah, she also needs to sit in a car seat as well. She wanted to fight back, but Tina quickly shut her down. As Tina sat in the driver's seat she turned for one last conversation.
"Now Leah, I know you said you wanted to act the part so that no one would know your true age, but do you know how to?"
Leah shrugged, trying to get comfortable in her new seating.
"I mean, how hard can it be? Just act like a dumb kid, right?"
"It's a bit more than that. People are going to be suspicious if you start behaving older than you should. Would you like some pointers?"
Leah scoffed, honestly not really seeing the big deal. Tina, however, was thinking she should give Leah a little help by commanding her. They decided...