Atsumu had been begging Osamu to go to the art-in-the-park thingy all week, they had been going to this festival every year since they were 12 years old, so really, he didn't have to beg that hard before the grey haired boy agreed.
The festival had always been a fun place and it had good food, and snow cones!! Osamu loved snow cones, knowing that, Atsumu promised to buy him one if he had agreed to go with him. They started getting dressed and Osamu hated the question he knew was coming. It got asked even when he wasn't little since Atsumu had the habit of dressing him anyway so there's no harm in asking. "Alright bug, I know you hate his question, but it's better to get it out of the way now so you don't have any accidents later." Atsumu started like he always did, "do you want a diaper or a pair of big boy undies?" Osamu cringed on the inside, "boxers." Osamu answered, Atsumu looked kind of concerned, "are you sure? You haven't gone to the bathroom since this morning and we'll be walking around for a few hours with only a porta-potty. You're 100% positive you wanna wear boxers bug?" Osamu nodded and Atsumu sighed but respected his decision, helping his brother get all of his clothes on correctly and then they were out the door.
Oh no.
Oh no.
He was in big trouble now.
They had been walking around for about an hour and Osamu started to notice pressure on his bladder after eating and drinking all of the snacks he bought using his allowance money. Atsumu should've stopped him. Stupid brother. Stupid stupid stupid.
It wasn't Atsumus fault though, Osamu knew that, Atsumu warned him a lot and kept reminding his twin to tell him when he had to go to the bathroom. In reality it was Osamus fault, he bought a bunch of drinks and sugary desserts. But Osamu was slipping, he wouldn't admit he was wrong this close to age regressing.
And then it happened.
He was humiliated and scared and so logically, he started crying. Sobbing even. The fox plushy he loved so much in his hands doing nothing to sooth him. Atsumu looked at his brother and immediately started freaking out, "what's wrong?? What happened??" Atsumu cursed inwardly as the grey haired boy started crying harder at the attention on him. He picked the little up and immediately realized why he was crying. 'Oh. That's why.' Atsumu thought as he rushed them out of the park and back into the parking lot, attempting to get them home before a full blown panic attack.
When they got home, Osamu's sobs turned into sniffles, he hadn't stopped crying when atsumu brought him inside, he just calmed down a bit. Atsumu immediately grabbed the stuff to clean him up, grabbing a diaper, wipes and a plastic bag to put his dirty underwear in. "I'm sowwy.." Osamu said on the verge of tears again. Atsumu softened his eyes and looked at him, "it's okay bug. It was an accident. Accidents happen" Osamu still looked heartbroken, "but y-you told me to t-tell you when I had to go potty bu-but I didn't.." it broke Atsumus heart to hear Osamu sound so humiliated. "Oh bug.. it's okay.. I'm not mad at you." He kissed his temple and they finished the process silently.
Afterwards, they watched Disney movies and ate all of Osamus favorite foods, some he didn't even know they could deliver to their house, but they managed it. And it all felt okay after that. It might've been humiliating, yes, but Atsumu made everything all better.
Atsumu always makes everything all better. That's just who he is. And Osamu couldn't be any more grateful. He really had the best twin brother ever.
