Izuku had never intended for things to end up like this. When the shrunken young hero had come up with the idea to gift himself to his mother Inko Midoriya for Christmas, having Ochaco put him in a tiny little box that she would deliver on Christmas morning, he had only meant it as a fun little surprise. And, at first, that's all it had been.
His mother had been as shocked as he had foreseen when she opened up the little box and found her dear son inside, standing at just two inches tall. Big, powerful fingers had pulled him from his box and dropped him on her open palm, where the middle-aged woman looked him over and made sure he was alright. She had calmed down considerably once he explained to her that he was perfectly fine, and that he would be back to his normal self in just a few more weeks once Mei finished gathering data on this shrink belt of hers; then she took to fawning over him instead.
“Oh, Izuku, look at how cute you are! You're just a tiny little doll for mommy, aren't you?” she said as she ran her motherly fingers all over his little body, playing at moving his little arms and legs and mussing up his little head while Izuku just smiled through it all. Normally he wouldn't have been too keen on his mom cooing over him like this and treating him like a little kid again, but it had been so long since he saw her, and he knew she was so lonely without him, that he was happy to let her enjoy her time with him however she wanted.
That was all pretty much exactly what he had expected of her, anyways. It wasn't until a little bit later, after she'd shared her breakfast with him on top of the kotatsu, that his visit started to take an unexpected turn.
“Oh, Izuku, since you're mommy's little present this Christmas, do you think you could do me a little favor?”
“Of course! Anything you want.”
“Are you sure? It's about my feet, see. I had to go out to the store yesterday, but there were so many people shopping for the holidays that I had to wait in line for hours! My feet still haven't completely recovered, so I was wondering if you could give them a little massage.”
“Er... you want me to rub your feet?” Izuku asked, tugging nervously on his shirt's collar.
“Is there something wrong with that?”
“N-no, no, it's fine. I'll rub your feet anytime, mom.”
“Thank you, Izuku!” Inko picked up her son and nuzzled him against her cheek, smothering him in her softness, then lifted up the kotatsu's cover and dropped him under it, where Izuku found himself between the two huge walls of flesh that were her warmed-up feet, toes wiggling and soles scrunching in anticipation of the service his little hands would provide.
Izuku sighed. He would have preferred not to rub his mom's feet, or to have anything else to do with them for that matter but she had been so eager for his help that he just couldn't say no to her. Besides, even if he had refused, there was no way he could tell his mom why he didn't want to rub her feet.
The truth was that Izuku had developed something of an obsession with giant feet ever since he first shrank down, and if Inko hadn't been his mother he would have been glad to serve them in any way he could. It was because they were related that he felt so conflicted about it. Inko's feet looked lovely, and they smelled lovely too, even if they weren't quite as attractive as Ochaco's—he didn't think anyone's feet would ever appeal to him more than hers—but he knew he couldn't let himself feel that way about his own mother's feet, so he made an effort to push down his obsession as he stepped up to her left sole, pressing his hands to the plush, wrinkly sole and beginning his massage.
Keeping his feelings under control was very hard after spending all this time indulging in them with Ochaco and the other girls, and it was even harder with how his mom's feet moved as he rubbed them. He did the best he could to make them feel good, and the soft moans he heard outside told him he was doing a good job of it; aside from that, though, Inko's plump little toes wiggled happily over his work, drawing his eyes to them every single time. They were very cute toes, and when he looked at their little wiggles Izuku couldn't help but imagine how nice it would be to have them wiggling all over his body.
Even so, he kept himself in check and stuck to rubbing Inko's feet by putting all his energy into his work so he wouldn't think of anything else. After a few minutes he had finished the first foot without incident and started working on the second, pushing his hands deep into her sole to knead away the tension in the muscles underneath. But his foot rub felt so good to Inko that by reflex she leaned into it by moving her foot towards him until she had caught him between her feet, utterly smothering him with her soles.
“Oh! Sorry, sorry!” she said immediately afterwards, moving her feet apart and pulling up the covers again to look in on him. “Did I hurt you?”
“N-no, it's fine, mom.” He wiped away a bit of foot sweat that had gotten on his face, mostly to try and hide how flustered he probably looked. “A-actually, you don't need to worry about hurting me. Shrinking made me more durable, so now it's almost impossible for me to get hurt. You could even step on me and I'd be fine.”
“Really?” For a moment Izuku thought he saw the spark of an idea in his mother's eyes, but if so, they were back to normal in a flash. Suddenly her foot started sliding back towards him, toes splayed wide to catch him by the waist and carry him outside. “Anyway, I hope you don't mind if we continue this somewhere in the living room so I can watch my show while you work. And so you can keep warm, you can stay right in here.” Inko carried him inside her slipper, dropping him on the insole while her massive foot slid over him and held down her tiny son, his face between her toes but the rest of him smothered under her sole. Izuku was shocked to feel his mother's full weight bearing down on him when she stood. The soft flesh of her foot pressed down on him, entrapping all his body save for his head which rested between her toes.
“Are you okay down there, Izuku? Touch my big toe if you are, and my second one if you want out. Hm? What's that? You can't move your arms? Well then... instead of touching them with your hands, just lick them instead!” she said, laughing at the thought of her tiny son licking her toes. She laughed even more when she actually felt his tiny tongue lapping at her big toe. “Did you really lick my toe, Izuku? He-he! I'm sorry, but it was just a little joke! I didn't think you'd take it seriously! Oh well, at least I know you're okay.” she curled her toes over his little head by way of a hug, then walked over to the living room, where she sat on the couch and left her feet resting on the floor.
Even when she was sitting down, the weight of her foot was too much to let Izuku keep massaging her, but to be honest Inko wasn't interested in that anymore. She was much more keen on keeping him underfoot and feeling her tiny son being smothered by her motherly soles.
Izuku was surprised to see how dominant she was all of a sudden. She kept him firmly trapped, never letting him escape her mighty sole, though she was content to let him crawl around under it as much as he liked, and especially under her toes, where she could play with the tiny boy as much as she pleased, wrapping her plump little digits around his body. She would have given much to make sure he stayed under her feet forever, protected from all harm by her motherly soles. Still, she knew she'd have to let him go back to his school eventually, so she resolved simply to make the most of him during winter break and never let him leave her side if she could help it. After all, her little boy was so tiny and helpless; he needed his mother to be there for him now more than ever, and to share her body warmth with him.
She kept him under her feet the rest of the day except to share her meals with him and make sure he was fine, and come nighttime she went to bed wearing the thickest pair of socks she could find, with Izuku trapped inside with her soles.
Izuku did all he could to resist his obsession, but there was only so much he could do. When halfway through the second day of being at his mom's feet he realized that she meant to keep him there for as long as possible, he decided for his sanity's sake that it was time to stop resisting and accept how much he loved being at his mother's feet. He loved being dominated by her plush soles and plump little toes. He loved how warm they were too, helping to shield him from the cold weather, and he showed his love by serving them even when she hadn't asked him to do so, vigorously rubbing her soles any chance he got.
“Oh, Izuku, what a good boy you are~,” she cooed at him one time when she woke up to the feeling of her tiny son servicing her foot, and she scrunched her sole in delight, firing him up even more. Her son couldn't help but to start kissing her soles in thanks for all his mother had done for him since he was born. Inko, too, was overwhelmed with love for her son, and she put her soles together in what she meant as a big hug for him, leaving him completely surrounded by her feet on every side. Then Izuku decided this wasn't enough, and he stuck out his tongue and started licking his mother's foot clean, much to her delight.
Izuku kept licking her sole for the rest of the day, all the while she carried on as normal, even going out to pick up with Izuku trapped snugly in her shoe, where he dedicated his whole being to servicing his mother's foot. Even when, a couple days later, Inko started feeling bad about not letting him out and she offered him the option to leave, he told her that he wanted to stay and do everything he could to make her happy. There was nowhere else in the world he would rather spend his winter break than at her feet.
Inko was so touched, she gave her little boy a big kiss and dropped him on the floor, right in front of her big feet, wiggling her toes to invite him over. Izuku jumped on her feet the first chance he got, worshipping them with his hands, his lips, his tongue even as they toyed with him, pinning him to the floor and smothering his tiny body. It was sad to think that he wouldn't be able to enjoy this once Mei had finished collecting her data and it was time to grow him back. Then again, maybe he didn't need to. Maybe he could convince her to let him shrink down from time to time. If so, he would be sure to ask her about it the next time he came home.
Giantess World
