I like this ship; it's cute. So here's a possibly very OOC fanfic for them. I obviously own nothing in this fic

Honestly, Izuku should've known way before now. There were so many obvious signs: All Might's lunchbox looked familiar, he had a spring to his step now, and he once straight up asked Izuku about his dad and if his mom was single! There was no reason he should've been half as shocked as he was when he found out.

After he started living in the dorms, he made sure to call home as often as possible, knowing his mom might worry about him alone. It became routine for them to check in with each other twice a week, telling each other about all the things going on in their lives so neither of them felt quite as lonely.

"Izuku...I got asked on a date recently." His mom awkwardly mentioned. "I went, and I've been seeing him a lot since."

"Really?!" Izuku hesitated before replying. Talking to parents about their love life just felt...weird. "What's he like?" It felt strange to ask but it seemed like the safest question.

"He's very kind and thoughtful..." He tried to imagine the mystery guy. Was it someone he knew? "He makes me very happy. Izuku, are you okay with this? If it makes you uncomfortable, I ca—"

"No! It's great!" Izuku hurried to cut his mother off, despite being uncomfortable. "If he makes you happy, then I'm happy for you! What's his name?" His mother hesitated.

"Yagi Toshinori." The name sounded familiar but it wasn't really ringing any bells. Toshinori...where had he heard that name before?

"Young Midoriya!" All Might cheerily clapped his hand on his successor's shoulder as they passed each other in the hall. "It's a great day! What's with that grim look?!"

"Oh, All Might. I'm trying to remember something I heard once." He replied distractedly, flipping through his notebooks.

"He's been like this all day..." Ochako shrugged. "Not even Aizawa-sensei could snap him out of it."

"All Might, do you recognize the name Yagi Toshinori?" Midoriya asked, not bothering to look up from his notes, his brow furrowed in concentration. He was so focused, in fact, that he failed to notice how All Might stopped and stiffened at the name.

"What about it, my boy?" Yagi asked, panic clear in his sunken eyes.

"It's the name of the guy my mom's dating...It sounds familiar but I don't know where I've heard it from..." Mic, who'd been walking past, exploded into a fit of laughter, only bothering to muffle himself when Midnight jabbed him sharply in the side, biting back laughter herself. All Might began to cough up blood in suprise, his face turning an odd shade of red.

"I...I must go! To teach! The classes with the, er, students! Yes!" He awkwardly announced, trying way too hard to sound casual (for his hero persona, anyway), before rushing off as quickly as he could. Only then did Izuku look up from his notebook in confusion.

"But it's lunch time..."

Every now and again, his mother would bring up the mysterious Yagi, a joyful ring to her voice as she spoke. He brought her flowers on a lunch date, rushed over because she was feeling sick, and finally, he recently told her that he loved her. His giddy mom spoke about him like a lovestruck teenager and he could instantly tell what she's said in reply to his declaration of love.

Regardless of if it bothered him or not, his mother was in love with her new boyfriend and actually planned for them all to get together at lunch next week. "So I finally get to meet my new stepdad?" Izuku teasingly asked, relaxing into the conversation as he would with a classmate, only realising his mistake after he made it.

"Oh, my!" He could hear his mother exclaim in embarrassment, "we're not quite there yet!"

"Yet," she said. "Yet." Izuku was so focused on that he barely listened as his mother continued to talk about how she met an old friend at the store and how they chatted about Izuku's UA life.

He also almost didn't notice how awkward All Might was around him, finding any reason to run away from any conversation and even avoided eye contact in class by staring straight up at the ceiling while talking. (It would've been too hard to ignore it after all.) But it took a very long time for him to connect the dots.

He was waiting at the café they chose for their lunch the day it all became clear. It was a nice day, the sun shining through the scarce clouds and the birds singing happily as the tree branches swayed in the spring breeze...and Izuku hadn't gotten even a wink of sleep. He stared out the window, bleary-eyed and suspicious of anyone who passed by. He smiled when he saw a familiar face.

"All Might! I didn't know you liked this place too!" Midoriya smiled at his mentor, too tired to notice how stiffly and awkwardly All Might was walking. Laughing nervously, All Might took a seat across from him, staring out the window. "I'm glad you're here! I'm really nervous about meeting my mom's boyfrie—" His mother walked in alone, grabbing his attention. He waved energetically, having had too many cups of coffee and frosted cinnamon rolls."Mom! All Might's here too!"

When she and All Might say next to each other, their faces red, it finally clicked.

All Might's lunches looked like his used to because his mom was making him lunch. He avoided answering his question about Yagi Toshinori because he was Yagi Toshinori. He was acting strange because he was dating his mom. He wasn't All Might's secret love child, he was his future stepson.

He stared at them wide eyed for a few minutes, making them both nervously fidget. "Oh, all that is mighty..." He accidentally muttered, so tired that he wasn't really aware that words had come out of his mouth.

After the first month or so, it was pretty great. Sure, having your teacher and idol as your possible new stepfather is nerve-racking as heck, but they got along well as a family. He wasn't at all surprised when Yagi proposed to his mother. In fact, he was pretty happy; it looked like he was finally going to get his Christmas wish from when he was four. ("I wish All Might was my new dad" sounded pretty impossible but amazing at the time.) Plus, now everyone called them the Mighty family. It was a joke at first but it really grew on them. Now if people stopped giving him a mini heart attack every time they called him Mini-Might, it's be perfect.

Especially since his mom was so happy with Yagi. That's what mattered most of all.

Deleted Scenes, I guess:

"I see..." Todoroki nodded after hearing Izuku out. "So All Might has finally decided to marry the mother of his secret love child. Congratulations." The way he smiled made it hard for Izuku to snap at him and once again tell him that he wasn't All Might's kid. He looked so genuinely happy for him!

He'd only told his close friends so far; Todoroki once again brought up the "secret love child" theory while Uraraka and Iida both congratulated him while also acting somewhat sympathetic to his anxieties. Honestly, he was so glad he told them...until Iida tried to do something nice for him and screwed it all up.

"All Might-sensei! I have a question that's unrelated to class!" It was rare for Iida to ask something off topic so All Might allowed him to ask, mildly concerned about the class president. "What are your intentions towards Midoriya's mother?!"

All for One couldn't take Yagi out but that question almost did.

These two are cute and need more love. More of and an Erasermight and AllEraserMic shipper but I still love these two. Can't write Todoroki at all, sorry. He feels pretty OOC there lol Hope you liked it!