Izuku and Hisashi arrived in the room to find themselves in front of a beautiful scene. A white-haired girl had jumped on Kai and grabbed him and Kai was returning the sign of affection.
Kai: Oh, you two did it. Izuku, this is my daughter, Eri Chisaki. Eri greets Izuku Yagi. He will probably move here.
Eri: Hi, I'm Eri. Pleased to meet you!
Izuku tough: PURE!
Izuku: Pleased to meet you Eri, I'm Izuku.
Kai: Introductions made. Now sleep.
Eri: OK dad!
Kai then accompanied Eri to her room.
Izuku: ... The great Overhaul, ruthless mafia leader and head of the eight death precepts has a daughter ... Who is the mother?
Chizome: She's not his daughter. Kai has always felt guilty for what he did many years ago. He killed the one who raised him because he was blinded by his anger towards quirks but when I met him he was already sorry for everything. When we found Eri in an alley crying he immediately ran to comfort her. Eri has a very special quirk called Rewind. It can turn back the time of anything it touches. He's very difficult to use and she accidentally killed her own Parents. Kai didn't even think about it for a second and adopted her, not legally since well, they wouldn't leave her to an ex-villain.
Izuku: Oh ...
Kai then left the room.
Kai: How are you still standing? I said sleep, remember?
Chizome: We have an extra room Izuku. Tomorrow, after taking the test to see if you really are Hisashi's son we will go and buy you a couple of clothes. I don't think you want to go back to that house.
Izuku: You're right. Night Kai, night Chizome, night Hisashi.
Izuku and the others then went to sleep. The next day all 5 went to take the test to verify what Hisashi had said and yes ... Izuku Yagi was the son of Hisashi Midoriya.
*after the exam*
The 5 came out of the hospital (I think we should take the exams of these things from there, I'm not sure) with a very happy Eri.
Eri: Now that we know that big brother is Uncle Hisashi's son, can he move in with us?
Izuku: ... Well, I haven't seen any signs or news about my disappearance, so why not?
Eri: Yeyyy
Eri then jumped into Izuku's arms and Izuku hugged her on the fly.
Hisashi: Well, as we said, it's time for "welcome gifts"!
Hisashi then double-looked around to make sure no one was there and then used a teleport quirk on everyone, taking all 5 to dagobah Beach.
Izuku: Oh god, is this place a landfill?
Kai: No, this was a beach.
Chizome: Well, it's time.
Kai: Izuku, as we told you, we would like you to take our quirks, in order to become the greatest hero ever. What do you say?
Izuku: I ... I don't know. You would be quirkless and then ... I don't think I actually want to be a hero. At least not anymore.
Chizome: You're right. Many agencies are corrupt and many heroes are fake ... But there are other ways to become a hero you know? You could become a vigilante, like me in the early days. The only other vigilantes I've ever known are Knukle duster, the crawler and Pop-Step.
Izuku: A vigilante? Do you intend to be against the law but to help people?
Chizome: That's what you want to do right? Helping people. You can do this whether the law is with you or not.
Kai: Well, why not?
Izuku: ... You're right Chizome. I want to help as many people as possible. And I will also do it against the law.
Chizome: This is the spirit. Now Hisashi, if you want to do the honors.
Hisashi: ... There is actually only one thing I need to add.
Kai: And what would that be?
Hisashi: Izuku, you've actually been through hell for the past 10 years and I can't help but give myself an art of blame. If only I hadn't left, if only I had continued to be with Inko, before leaving her to avoid putting her in my villain problems ... You wouldn't have been through this. For this reason and to redeem myself from what I have done and at the same time, I give you ... MY quirk.
Kai and Chizome: WHAT!?
Izuku: A-all for One?
Hisashi: Right. You see, my quirk, as already explained, allows me to steal, use and gift quirks, and well ... I can gift my own quirk too! I'll keep my other quirks though.
Izuku: Are you sure d-dad?
Hisashi then escaped a smile.
Hisashi: Much more than sure, son.
Izuku: Right. Then I accept your offer!
Chizome: Well, let's do it.
Hisashi then put a hand on Izuku's head, giving him All for One.
Izuku: Well, that was easy.
Hisashi: ... strange. It's as if All for One is too small for your body.
Izuku: What ... What do you mean?
Hisashi: In the exact moment I gave you All for One, it's like it has adapted to your body. It has improved to be accepted by your body. Such a thing had never happened before.
Kai: Has it improved?
Hisashi: Yes, but I don't know how.
Chizome: In any case, Izuku, I have prepared a training plan to improve your physique.
Izuku: Wow, this pattern even has hours of sleep!
Chizome: Only the best for our successor.
Hisashi: Well, now comes the hard part. Izuku, to activate All for One you have to imagine yourself as a flame, present within you. Imagine running it all over your body, and then your hands.
Izuku then closed his eyes and almost naturally glimpsed a flame. Pushing it all over his body, Izuku opened his eyes to see a green flame come out of his hand. Izuku then touched both Chizome and Kai with the flame on his hand.
Hisashi: Ah, that's how it improved. Now you are able to steal quirks just by touching someone.
Kai then touched a nearby refusal and nothing happened.
Kai: Well Izuku, now try to imagine the scene. You touching a computer and it is reduced to atoms. Try to do it with something here, it's all garbage.
Izuku then touched a computer and it disassembled.
Chizome: All for one, Stain and Overhaul have a successor. I already see the headlines when you will make yourself known to the public!
The 4 then shared a laugh as Eri fell asleep in Kai's lap (Kai is best dad).
* With the assholes AKA the Yagis *
Izumi just woke up.
Izumi: It's a beautiful day outside. The birds are singing, the flowers are blooming. Perfect for some tea!
Now you'll all be like "Oh my god, Sans?". Well NO. This is the phrase that Asgore says in pacifists and neutrals.
Toshinori also just woke up and Inko had just finished making breakfast. The three then gathered in the kitchen to eat. After eating Izumi went to school. It seemed to him that something was missing but he couldn't remember what. Once she got to school she met her friends and then entered the classroom. Only once the lessons started did he understand what was missing.
Teacher: Izuku Yagi? Absent? Oh well ...
Izumi then recalled that she hadn't seen her brother since the day before.
Katsumi: Izumi, are you okay?
Izumi: No.
Shoka: What happened?
Izumi: ... I haven't seen Izuku since yesterday. I have no idea where he is.
Shoto: Did you check his room? He'll probably be sick.
Izumi: I hope so.
At the end of the lessons the whole group went to Izumi's house and then headed to Izuku's room. Empty. Izuku was not in his room. There was no ticket, nothing. The only thing they found except all the All Might postrs and stickers was a razor, stained with blood.
Izumi: ...
Katsuki: We have to tell your parents, at least they'll stop him when he gets home.
Shoka: Right.
Everyone then went into the room to come face to face with all their families.
Enji: Ah, guys, are you all here? Toshinori and I have decided to have a reunion (Yes, Enji is best dad along with Kai).
Izumi: Mom, Dad ... Izuku wasn't in school and he's not like her. We don't know where he is.
Inko: What? Toshi, where could he have gone?
Enji: Don't worry, I'll find Izuku, I assure you.
Rei: I'm coming with you Enji.
Mitsuki: I'm going to see around the house. You Toshinori stay close to Inko.
Toshnori: Sure.
Izumi: ... Plus ... we found this.
Izumi then took out the blood-filled razor. Inko, seeing the razor, began to cry while Toshinori was left speechless.
Inko: When ... When was the last time we spent time with Izuku?
Toshinori: I ... I don't remember.
Izumi: It was our fault.
Shoka: After learning that Izuku was quirkless, we started bullying him into trying to make him give up his dream of becoming a hero.
Katsuki: We were scared that he might die.
Inko: It's also our fault. We disowned him ... only because he was quirkless. We are the worst parents ever.
Toshinori: What matters now is not to blame. We need to find Izuku, and apologize to him ... everyone.
Shoto: You're right. I'm going to look in the forest back here.
Everyone then parted ways to look for Izuku.
Meanwhile with Izuku.
Izuku was watching reddit (r/memes) on the new phone Hisashi bought him (Hisashi is fucking rich) when suddenly news of him disappeared appeared on his home page.
Izuku: Oh, they noticed.
Chizome: Thank goodness! It took them only 2 days to realize that their own son was missing.
Izuku: I don't consider them my parents anymore. The only relative I have is you dad.
Hisashi: I love you too son.