ABO fics are a weird guilty pleasure of mine, but I'm really annoyed about it mostly being smut and consent issues. It's an interesting concept and I wanted to expand on it in a way I hope is ok

-Omegas
Izuku, Kirishima, Kaminari, Asui Tsuyu, Ashido Mina, Yagi Toshinori, Present Mic
-Alphas
Bakugou, Yaoyorozu, Jirou, Ojiro, Todoroki Shouto, Aizawa, Shinsou, Midnight
-Betas
Tokoyami, Iida, Uraraka, Satou, Sero, Mineta, Hagakure, Kouda, Aoyama

Edit: Changed Midnight's and Present Mic's designations

"I want to try out in the UA entrance exam next year." Shouji said.

Three pairs of eyes locked onto him from across the table. One pair immediately narrowed in disapproval, the other two wide with surprise, but also proud acceptance.

His mother, the owner of the single pair, tutted. "Now, Mezou, we've talked about this. It's just not appropriate for an Omega to be a hero. You've been listening to All Might's interviews again, haven't you?" She spat out the name of Japan's Number 1 hero as if it were rotten.

Shouji clenched the fist of one of his extra arms under the table. His mother was extremely traditional, though she herself was a Beta and had married his Alpha father, she somehow still maintained the old views of where Alphas, Betas, and Omegas fit in society. She was determined to have Shouji be the perfect Omega, despite how much he didn't match that view.

"Now, now. Shouji would make a great hero!" His father interjected, his dual mouths pulled into a bright smile. Shouji definitely took after his father more, he had his mother's straight white hair and had inherited the multi-armed Quirk from her, but he had his father's tall, muscular build, dark eyes, wide mouth and sharp teeth, and his father's ability to swap body-parts had transferred over into Shouji's ability to transform the ends of his extra arms.

"Look at him! He's strong, he's got a good head on him, and his Quirk would be great for reconnaissance and rescue!" His father continued, and Shouji had to fight a delighted blush at the praise. His father had always been his greatest supporter. Any sport or club he wanted to join, when he'd become interested in joining his father in the gym, he'd even join Shouji and his mother when she started teaching him how to cook and sew after he officially presented. His father was horrible at the latter two, but Shouji appreciated it all the same.

His mother sneered. "I still do not understand why you ruin his figure like that, no Alpha is going to want him when he's so bulky!"

He really wanted to tell her that he had no interest in Alpha's, but he knew it was a lost cause. She'd ignore anything he said or tell him that he was "still young, you'll feel different when you're older".

Sighing, he finished off the last of his food and asked to be excused. His mother waved him away and his father shot him an apologetic glance, which he returned with a weak smile as he cleaned up his dishes and went to his room.

He collapsed on his bed, staring up at the ceiling for a few moments before rolling over and grabbing his old laptop, one of the few personal items he had, and even then it was mostly used for school.

He went on HeroTube and clicked a video from his Watch Again list, after some buffering a slightly younger looking All Might appeared, sat alongside a talk-show host.

"So, All Might, what are your thoughts on Omega heroes? Do you think their dynamic lessens their effectiveness?"

All Might sat up straighter. "Of course not! It doesn't matter what dynamic a person is! Omega, Beta, Alpha, anyone could be a hero!"

A knock on his door caught his attention and he paused the video to sit up.

"Come in." The door opened and his father peeked in.

"Hey." He greeted, slipping into the room and shutting the door before sitting on the bed beside his son. "I'm sorry, Mezou, about what your mother said..."

Shouji shrugged, looking down at his lap. "I've gotten use to it... I didn't really expect her to suddenly change her mind.."

His father sighed and put an arm around his shoulder. "I wish she'd see how wonderful you are, Mezou. You're so strong and you have a big heart, being an Omega doesn't change that at all."

Shouji huffed. "Sometimes it feels like you're the only one who thinks that..."

His father frowned. "Kids at school giving you a hard time again?"

He nodded hesitantly. "I've been keeping the mask on and eating with my Quirk more because they still keep comparing my teeth to villains.."

His father pulled him into a hug, tucking his head in the crook of his neck and rubbing his back. "I know it hurts now, but just think, when you become a Pro and have tons of fans, they'll be praying to get even a quarter as good as you are."

Shouji chuckled wetly, pulling back to look him in the eye. "When?"

Both his father's mouths pulled into even toothier grins. "Yeah, when. Because you will. You'll be a great hero, and I'll brag to everyone that my son is a Pro. I'll shout it from the rooftops and get banned from every building because people will get so sick of me saying how proud I am of you."

Shouji laughed and pushed him away. "Ugh, please don't, I'll never set foot back here again. I'd probably leave Japan altogether."

His father laughed and ruffled his hair as he stood. "I'd follow you, no matter what your mother says."

He smiles. "Thanks, dad."

The smile's returned two-fold. "Of course, Mezou. Now, get some sleep, you have school tomorrow."

Shouji nodded, putting the laptop away and laying down as his father flicked off the lights.

"Goodnight, dad."

"Goodnight, Mezou."

In my ABO universe Male Omegas and Female Alphas are intersex with internal testicles.

Male Omegas have weak but viable sperm, Female Alphas weak but viable eggs.

Male Omega can impregnate other Omega and Beta Females, and Female Alphas can get impregnated by other Alphas and Beta Males, either requires more effort than a typical Alpha/Omega or Beta/Beta pair would. However Omega Males impregnating Alpha Females is extremely hard and usually requires medical assistance.

Full heats occur every three months. Symptoms are: High fever, extreme anxiety and over-sensitivity, and weakness. There is no loss of control and arousal only occurs when they feel safe and are with a chosen heat-partner or mate. The only 'sexual' thing about it is that their fertility is heightened.

Omegas have pseudo-heats that happen once or twice on a month, or it can be triggered by outside factors. Symptoms are: Anxiety, heightened emotions, dizziness, sensitivity to light and noise. Fertility isn't heightened here, they just want to be close to their pack.

Alpha Ruts can be caused by a number of random factors and last in varying lengths and intensity. Symptoms: Possessiveness, aggression, over-sensitivity, anxiety.

I think that's about it. Questions are welcome. A picture of Shouji's parents is on my Ao3 Barely_Coherent_Zombie.