A devious thought came to Tina's mind. Maybe she can keep Leah in diapers without altering her mind, just command it---if she makes it so Leah has to go whenever she feels the need, she'd technically be going on purpose. Just like in the car, she'd be powerless to stop herself from going in her pants.
It was incredibly mean to Leah, but the thought of her looking embarrassed as she has to suddenly unload in her diaper was too cute to resist. Tina will make it an experiment, something to keep for a week at most. She shouldn't be doing it in the first place, but she figures a little fun on Leah's behest couldn't hurt her (in the long run, anyways).
As Leah raced to the bathroom, Tina had time to plan. She was cooking dinner by the time the teen came back down.
"Did you put on training pants?" Tina asked, getting an embarrassed scoff from Leah before she lowers her pants enough to show the pull-up underneath.
"Yeah, I want to avoid...anything else." Leah replied. Tina smiled.
"Leah, whenever you feel the need to go to the bathroom, you will go potty in your pants immediately until the feeling goes, pretty please."
The statement was a bit longer, getting a confused look from Leah before her eyes glazed over. Coming to, her brow creased as she noticed something different. Her eyes widened as she crouched forward to pee. In her head, she was peeing herself on purpose, but couldn't actually stop herself. The flash of emotions that cross her face was certainly something to see: from shock, to panic, to shame, to miserable acceptance.
"Something wrong Leah?" Tina asked, making Leah jump.
"Yeah, everything is fine."
"It sounds like you're going pee pee."
Leah flushed red, not able to deny it.
"I...um...yeah."
"Could you not make it to the potty, sweetie?"
Leah was silent, trying to come to grips with that face that she's purposely wetting herself involuntarily.
"I guess not."
"It's alright. You're just having a little trouble right now. We'll work on it." Tina said with a smile, knowing full well that nothing they do would help. Tina is definitely being mean here.
"Yeah, I guess."
"Dinner's ready! We can get you changed afterwards." The two sat down at the table, Leah still mortified by her lack of will power. The two ate silently as they always do, with the added bonus of Leah peeing herself multiple times. Even the slightest tinge in her bladder would force her to push, and Leah was clearly unsettled by how willing to pee herself she is. It wasn't until their plates were near empty when Leah scrunched her face and farted.
"Goodness Leah! Excuse you." Tina teased, causing Leah's face to blush brightly. She opened her mouth to comment, but grumbled as she squirmed in place, intentionally leaning to the side and grunting to push out a longer, more airy fart.
"Leah, table manners! You'll stink up the room at this rate!"
"I-I can't help it!" Leah cried, despite lifting her butt off the chair to very obviously push out another bubbly fart with a wet end.
"Leah, you clearly pushed that out on purpose. No one minds you being a little gassy, but at least be polite about it." Tina calmly replied, once again making the teen blush indignantly. She has nothing to say, because it's neither on purpose or an accident, and Leah's not sure what to blame. She quickly finishes her plate after that, and rushes off.
"Where are you going?" Tina asked, but Leah pays her no mind. Her demeanor seem off until a gassy squelching inflates the back of her pants. Leah looks behind in grim acceptance as she squats and finishes pushing mush into her training pants.
"Oh, you almost made it. That's good! That means you could feel the need." Tina commented cheerfully, making Leah blush further, "Although that looks like quite a bit of poopy. We might need diapers if you keep having these big accidents."
Leah shut her eyes tight, red to the tips of her ears.
"Go ahead and get a shower. I'll diaper you after you're done." Tina stated, prompting the teen to follow without another word. Tina had to admit, seeing Leah be a shy potty pants was enjoyable. Horrible, but enjoyable. Should Tina keep going with this? Afterall, Leah was embarrassed but not distressed...she hoped. Plus, having Leah be diapered for a bit, and purposely using that diaper, was incredibly cute. For Tina. It's hard to justify what's essentially gaslighting her stepdaughter. Tina was really started to get worried about how willingly she overwrote Leah's will; there will come a point where Leah with either figure it out and never forgive her, or be damaged beyond repair. Was there even a way Tina could use this control she has over her stepdaughter in a good way? Tina scrounged her head for what to do, and decided to...