Sitting alone tinkering away at some gadget she made on a counter Mei Hatsume happily had her magnifying glass strapped to her forehead. Her next invention was almost complete and Mei desperately wanted to test it out. Finally it was finished, Mei held up her device which was not electrical at all in fact it was a diaper. Mei made it specifically to fit loads and loads of shit in it but now the only thing she needed to do was test it out. Mei rubbed her chin and thought of the perfect plan.
 "I'm sure a couple ladies from Class A can help out" said Mei
 Mei whipped her phone out and found Momo and Toru Hakagure's numbers. It wasn't too late so they shouldn't be asleep plus they were in the dorms not too far away. She sent a text to both to have them meet her in the lab room. They responded within five minutes of each other both heading her way. Mei smiled and removed her goggles and her baggy pants and panties. Mei made sure the diaper would fit comfortably over her large rump and it did perfectly. The diaper slid on no problem and it was nice and snug. With that done Mei went over to a hiding spot and as she quickly moved her boobs bounced in her black tank top. As she hid though some other ideas came to mind. A pill she made would let her anus expand and this is a perfect time to test it. Quickly she goes and gets the pill and pops it into her mouth. A gulp sends it down and she can feel her ass loosen up. She went back to hiding and removed her diaper as her asshole is going to be needed. Finally a knock came at the door and Mei crouched down. It opened and Momo walked in all by herself.
 "Hello...Mei...Toru should be here in about ten minutes she needed to get ready and take her time so I just came by" said Momo
 Mei felt lucky and she didn't even need to hide yet. Mei stood up behind the machine she was hiding behind and waved.
 "I'm glad you made it can you come and help me out testing this new thing" said Mei
 "As long as it doesn't explode" said Momo
 "Well that would be a pain to clean if it did" said Mei
 Momo didn't pay too much mind to that and went over. Momo was wearing her gray UA clothes and looked stunning in them. Momo came to stand next to Mei and was surprised to see Mei half naked. Momo looked away and saw the baggy pants were gone. As she was going to ask what's going on, Mei's hands landed on her shoulders. Momo is forced to face Mei who has a smile on her face. 
 "It will be easier to get the invisible one up my butt so you're gonna have to settle being swallowed" said Mei
 "Wait...huh" said Momo
 Mei's mouth then distended and unhinged opening wider than Momo had ever seen. The inside of the wet mouth surprised her and all of sudden her face felt warm and it got very dark. Mei had shoved her head inside the dark wet maw. Momo just stood there in complete awe feeling Mei's tongue brush against her face and her hair touching the back of Mei's throat. Finally the sound of a gulp came and Momo yelped as she was dragged into the tight throat. Now aware of the situation Momo squirmed to get free but it proved useless as the lips got around her shoulders and Mei was making easy work of her. Mei slobbered on Momo's breasts, squishing them with her tongue as they entered her mouth. They were nice and squishy but Mei needed to hurry up before Toru came by.
*gulp..gulp...gulp*
Momo tried hitting Mei but the more Mei swallowed the less mobile her arms were. Momo was lifted off her feet as her belly button was gulped. Mei had cupped her hands over the nice ass of Momo feeling it squish in her hand. Mei continued getting the hips and large butt down her throat leaving only the legs to go. Mei tilted her head back while holding her already swollen belly as each gulp made it get bigger and bigger. 
*glrk...gulp*
The thighs were gone and the legs flailed in the air until Mei was pushing down on Momo's feet. But a pair of shoes were in the way so Mei took them off and tossed them by her pants and pushed the feet down. Her mouth shut and a final strong gulp sealed the deal.
 "Ahhh..what a satisfying meal...of course Toru's gonna join you soon enough" said Mei
 Mei gave her belly a pat which had the shape of a person upside down in the fetal position. Momo ended up being head first in the small pool of acids. She cried out and squirmed to position herself better. But all she could muster was having her back against the acid. Momo whimpered and pushed back the walls making air shoot up Mei's gullet.
*bwarrrpp*
Mei belched and came from out of the machine's corner and waited for Toru next to the door. Finally Mei heard footsteps and in came a UA suit with no one in it.
 "Oh Mei, Momo sorry it took me so long but I'm here now" said Toru
 She looked around at the counter and saw no one. She then looked down to see Mei's pants and Momo's shoes which had spit on them. Toru went to them and crouched down picking the shoe up.
 "I didn't come to a weird orgy did I" said Toru
 Unknown to her Mei came from the shadows of the door and stood up behind her ready to test her pill out. Mei turned around and sat on where Toru's head was. Mei had spent a lot of time with the invisible girl so it wasn't so hard finding her head. Toru's confused yelp was swiftly drowned out by the anus walls as her entire head was sucked in. Toru tried reaching her hand up and was grabbing at the fat ass cheeks to try and push them off her but it seemed pointless as nothing happened. Plus the fact Mei was already going down Toru's shoulders limiting her arm movement a lot. Mei moaned feeling her asshole opening up so much. It seems the pill she made worked perfectly as her asshole went down the breasts. 
 "What the hell is this..it smells and I'm stuck in something" said Toru
 Toru still really had no idea what was actually happening. All she really knew was it was smelly and tight. But Toru did hear faint moans that sounded like Mei. Mei finished half of Toru and stood back up letting the second half dangle out of her ass.
 "Wow my pills are working amazing...I might have to make many many more" said Mei
 With that her asshole inched down Toru's ass slurping it in leaving only the legs left. 
*shlck...slurp*
The legs were dealt with easily and the shoes fell off Toru's feet before the anus shut. Mei stood straight feeling Toru in her guts and finally inside her stomach with Momo. Now both Momo and Toru were squirming for their lives within Mei.
 "Momo what's going on where are we" said Toru
 "Mei's gone crazy and she ate us whole" said Momo
 "What...noooo" said Toru
 They pushed the walls back as stomach acids started to pour from the walls and pool at the bottom. Their bodies covered in sticky stomach acids and their school uniforms started to get ruined.
*bwarrrrppp*
Mei belched and two panties came out covered in stomach acid. Mei looked at them and figured the red ones were Momo's and the pink one with a teddy bear on it were Toru's.
 "Thanks for helping me with first one..now I can't wait to dump you into my special diaper I made" said Mei
 "Wait...diaper..do you mean you're going to digest us" said Toru
 "Yep that's the plan...I need you girls to become loads of shit for me" said Mei
 They both cried out and went into another fury of struggling. Momo and Toru's face were pushing up against the walls and Toru was actually visible from the outside. Her curvy bulge easily seen which sorta made Mei smile. Mei rubbed her large tummy and pinched Toru's ass. Toru yelped and kept fighting Mei's belly.
*groan...churn*
The girls clothes were in strands falling off their bodies and dissolving in the pool of acid. The walls were getting tighter forcing Toru and Momo even closer together making them yelp. Momo tried her best to ignore the stinging sensation of Mei's stomach acid but it truly was not pleasant. Mei went ahead and slid her diaper back on as the pair of girls were digesting nicely and it would be pretty soon until the test officially would happen. 
*gurgle...blorp*
Momo and Toru felt all mushy and gross now as they were melting into the rising slurry. Toru weakly pushed up against the walls which now was going absolutely nothing but breaking her down faster.
 "Momo...I think...this is...it for me" said Toru
 Her invisible body sank under the large pool and Momo felt Toru breaking under her. The acid was to Momo's neck and she cringed a little. With only her head and legs out of the acid her midsection was all goopy and falling apart.
 "Damn...it" muttered Momo
 Momo shut her eyes as the acid reached over her face and it was over for her. The last remaining bits of Momo fell into the acid as her body came apart. The last human looking bulges were gone leaving a nice round sloshing gut left. Mei poked and squished her hand in listening to the mush move around
*slorsh..crack..slosh*
The girls were all done and digested and finally they were emptying into the guts. Mei pushed her belly down as it shrank. Fat ended up in her breasts making them even bigger as well as her ass making the diaper a bit tighter but still nice. Mei smiled and poked the small jiggling fat left.
 "Alright ladies let's see if my new invention worked" said Mei
 Mei felt her bowels fill and she crouched a little and pushed. The soft crinkle of her diaper sounded as the warm wet crap was being pushed into the diaper. Mei moaned feeling the logs continued to fill her diaper up. It expanded and turned a brown color but it didn't break. Bones started to come out and poke at the diaper but it didn't break then either. It just kept going and going, filling up more and more. Skulls bulged against the diaper walls being clearly visible.  
 "Not much left but the diaper seems to be a huge success" said Mei
 Mei grunted shooting out the last few turds out of her asshole and it was done. The diaper ended up being the size of a beanbag chair and there was no sign it was breaking.
 "Yes yes yes it didn't break...now I wonder how much until it breaks" said Mei
 Mei giggled and pulled her phone out, seeing all the other girls' names in her contacts that could be valuable test subjects for her diaper.