The first time that Izuku writes the letter, there's only one. He puts it in an envelope and writes "In case I die" on the front. He didn't really think about the fact that his mum definitely would've opened it regardless, with that label. He puts in his desk drawers, though, and his mum isn't in the habit of rummaging through his things. He's twelve years old.

Mum.

I'm sorry. I know that if you're reading this, I've done something selfish. Or maybe I just got unlucky. Regardless of what happened: I'm sorry. From here on, I'm assuming I killed myself. If I didn't, well, know that I'm not too upset with how things ended.

I've been thinking about it for a while, and I'm kind of just expecting to do it eventually, at this point. Figured I'd write a catch-all letter and make sure that you have something to explain it.

It isn't your fault. You are probably the least to blame of everyone. I may not be social, but I know how to research. I already looked up the signs, memorised them. I won't be showing any if I can avoid it. Once I finally commit to it, I'm gonna make it foolproof. We both know that I wouldn't give you a chance to stop me. Don't try to convince yourself that there was one. I don't want you to hurt.

Just... move on, I guess. Know that I love you and I wish I didn't have to do this to you. There isn't a place for me in this time. I have an impossible dream. There's nothing that's both realistic and a life that I could enjoy. The only one to blame is my shit luck and the society that made sure there wasn't a place for me. Not you. Never you.

I love you.

—

The second time that Izuku writes the letter, there's three. He rewrites the one to his mum, after pulling it out and realising how much that would've scared her to find. He ends up putting each in their own envelope, and then all three in a larger one labelled "If something happens". Vaguer, but he knows they'd still open it if he died or was kidnapped. He knows about All For One, now. He knows what's at stake. He's fifteen.

Mum

I don't know exactly what happened, so I won't speculate. But if you're reading this, I'm gone. Talk to All Might if you can. He knows a lot about me, things that I can't tell you about. You deserve to know them now.

He'll tell you if you need to hide. If he isn't around, assume that you do. Run. Change your name. Avoid anyone who can give or take quirks. I'm sorry to put this on you. You deserve better, but I've never been able to turn away from what's right. And fighting this battle is right. I just wish it didn't come to this.

Talk to Kacchan as well. He'll need the support, and you'll need the family. I know I'm all you had. I'm sorry.

I love you.

All Might

I'm assuming All For One got me. Could've been someone else, I suppose, but he's probably involved. I'm sorry that I left you. Please don't blame yourself. I know you. I know you'll try, but I need you to carry on.

Keep my mum safe. Help Kacchan. Don't lock everyone out.

And even if getting One For All ultimately leads to my death, it was worth it. You were the first person to really believe in me, and I can't put into words how much that means. I care about you. You've been more of a father than mine ever has. I wish we had more time.

Don't let my death become yours

Kacchan

Yes, those are strands of my hair taped to the letter. Eat one. If it works, I'm giving you my quirk. If you really don't want it, I don't care if you give it to someone else afterwards. I trust your judgement.

Talk to All Might, Gran Torino, or Naomasa Tsukauchi. They can tell you more than I can. Short version: You'll be the tenth holder of One For All. It's a transferable stockpiling quirk. All For One is a villain who can give and take quirks. He's probably the one who killed me. Protect my mum, protect yourself, and protect your family. You'll all be at risk.

I know this is a lot. I'm counting on you to be able to handle it. I need you, Kacchan. I need you to be strong enough for this.

I never stopped admiring you.

—

For a while, Izuku forgets about the letters. All For One is in tartarus and things are going okay. He tosses the envelope onto a shelf when he moves into the dorms, but it's an afterthought. He lets himself get caught up in training. Then Shigaraki merges with All For One and Izuku leaves UA. He sneaks the letters into his mum's things, slipped into the folder of documents that she keeps safe but rarely looks at. It isn't perfect, but it'll do. He adds one more letter. He's sixteen.

Aizawa

I debated whether I should write you a letter at all. You've been so important to me but I don't really have any final messages or important information for you. I'm being illogical. That shouldn't surprise you.

But you, our class, it's become a family for me. It's the first place that I've really been accepted. I didn't want to leave you with nothing.

My classmates will need support. I wouldn't give our bond for anything, but that also means that a loss will only hurt more. I hope they'll band together, support each other. Keep an eye out for anyone who doesn't.

And please, don't shoulder any guilt for what happened. I can't know how it went down, but I do know that you did everything you could. You were the first teacher I was able to trust. You've been a rock for me, whether you realised it or not.

Don't go this alone.

—

That's how the letters stay, for over a year. Over a year of chaos and all-out war. It does end, eventually. Society isn't as strong as it once was, and grief is ever-present. But it's over. Izuku is just another hero. A well-known hero, after everything he got involved in, but just another hero. No more legacy weighing him down, forcing him to keep track of his letters.

He slips the envelope out of his mum's things when he grabs his birth certificate, age verification for his full hero's licence. He doesn't throw them away, not wanting to tempt fate quite yet. But he does throw them in a desk drawer, allowing himself to forget about them.

After a while, after he's settled into being a hero without an immortal supervillain gunning for him, he stumbles on the envelope, buried under forgotten paperwork and covered in dust. "If something happens." Hah. Something happened all right. He survived. He burns the letters. He's twenty-two.