AN: I have a serious writer's block going on concerning the events of the main plot, so after a bath of inspiration I decided that it was high time to write the backstory of Corrosive.

Chapter 21:

Danzo Akira was born on July the 13th, on a Friday, the same year as Enji Todoroki. His father was Hanzo Akira, while his mother died in his birth. This caused his father to fall into depression, which got worse and worse the more Danzo grew. While he was a baby, and then a toddler, his father was if not very good, at least acceptable. He was fed, and while they did not have many interactions that weren't filled with the melancholic air that hung around Hanzo, they were still fine. However, due to the time he spent away from work, Hanzo was fired from his job. He couldn't find another one, and soon alcoholism gripped him. While drunken, whenever looking at his son he would be reminded of his lost wife, and he would often fly into rage, which resulted in Danzo getting beaten. He learned to avoid his father then.

After a couple weeks of drinking all day, money began running short, and so even though it was previously unimaginable for him, Hanzo became a villain. Just a small one at the start, robbing stores to get money and food. Sometimes Danzo would spend days alone at home, waiting for his father to break out of jail when he was once again locked up. As the years went by, he became began to grew as a villain, the scale of his crimes increasing, getting locked up for longer and longer. Danzo would often have to go out and steal food in order not to starve, since he would eat everything that was at home. When Hanzo came back months later, he was always enraged at the state of the apartment, and once again he would become violent, even using his quirk on his son. It was nothing really special, the apartment wasn't filled with grafitis on the wall or anything, but Danzo wasn't able to properly clean it. In his father's eyes, these small imperfections turned into so much more. What a quirk it was. One of the greatest wind manipulation quirks, wasted on such a horrible person.

Thankfully, Danzo was a smart boy. He inherited his mother's smarts, and he would often sneak in her study which his father avoided at all costs, reading the books she wrote which were extremely coincidentally books written with her own 'better teaching method for children'. The themes of the books ranged from reading, to math, to all sorts of different things. It was there that he tried to forget about his world, and learn about the big one outside. It was true that he could have just run away, but he was convinced that his father would find him and kill him for good. He didn't want to die.

His favorite book, by far was the one detailing how children should train with their quirks. It was generalized, but it provided examples for all kinds of different quirk ideas. There was however, one part excluded from the final release, however he found the notes in her drawer. It was talking all about the quirk of her potential future child, detailing everything she could think of. The last one was actually his own quirk, though the foreword of that part was „This quirk would be the best possible combination of Hanzo's quirk and mine, so with my terrible luck it probably won't happen. But just for fun, let's write about it. :)" It was those notes that changed his life.

When he was eight years old, his father went missing, and after a month, Danzo decided that he must have been locked up permanently this time. During those months, he went out and made friends, spent his live living without fear and generally had the time of his life. Then, after four months of peace, his father returned. He was furious. He was convinced that Danzo snitched on him, and that's why he was caught. He was then locked into his room, and told that if he came out it would be the end of it. That's when he snapped.

His acidic mist up until that point wasn't very strong. He could create little, and was easily injured by it. However, after the breath of fresh air he experienced, he couldn't go back to living in the shadows, waiting all day long for his father to calm down so he wouldn't be hit just for showing his face. All the anger built up over the years was let out, like air from a balloon.

The entire apartment became filled with acidic mist, it's potency increasing rapidly. His father tried to blow it away, but it wouldn't move. His skin began to dissolve, and screams were heard in the entire neighborhood.

Later, the police would find Danzo and the remains of Hanzo in the same apartment, both of them in the same place. Thankfully, the police had an investigator with a quirk who could find out the indentity of anyone based on a bone of their corpse. Danzo was excused, since he was still a child, and then he was entrusted into the foster care system. There, his new goal formed. He remembered how his father broke out of jail so many times, only to come back to hurt him. He enjoyed the freedom he felt now that he wasn't alive to torment him any longer. This is why he decided to become a hero, so he could do what all the others are too afraid to do. To really save people, to make their lives better and not just lock away the problem temporarily.

He was able to get into UA, into that year's class 1-A. It was the same class that Endeavor was sorted into. In school, he was reclusive and quiet, always focused on becoming better. He was often berated by the teachers for his brutal methods, yet he continued using them, just in a more secretive way. Every day he would remain after school, and use the grounds to train with his quirk, increasing the amount of mist he could generate and his tolerance to it. This is how he spent the first couple of months, but it all changed during the Sports Festival. The first task was aced by class 1-A and class 1-B, while even some of the general educations and support students also succeeded. For the second task, students were required to form teams ranging from two to four members. He just sat in the corner, waiting to spot a team where they would tolerate an outsider like him, since that's how he felt like. He was surprised then, when he was approached by the best student in class, Enji Todoroki.

„You are the only one I see who takes this seriously, not as some sort of childish games. I need at least one teammate, and you're better than the rest." Their friendship started that way, though it didn't look like that at the time. After the second round, they needed to fight each other in the third, where Enji won thanks to his mobility and ranged attacks with his fire.

He won the sports festival, and stood like a prince on the podium. It was to everyone's surprise however, when he and Danzo began to train more together. Endeavor wanted to be number 1, and Danzo wanted to be the best possible hero. Both of them took it seriously, and they motivated each other even more. They were rivals.

After starting hero work studies, they worked as a duo, one of the most effective ones ever. Enji was their face, while Corrosive was only his shadow. He was fine with that however, he didn't want fame. He wanted to purge the world of the criminals. Slowly, a rift started forming between them. The murders were recorded, and their place on the hero list wasn't increasing.

„I want to be the Number 1 hero, no matter what!" said Endeavor when they parted ways. Despite that however, their friendship still went on. They met up sometimes, and discussed hero work. Life went on, right up until Endeavor's wife was shipped into a mental hospital. He immediately wanted to console his friend, to ask how he could help. The answer shocked him.

„She should stay where she are, she distracted Shoto from training. He is going to become the Number 1 hero, and cuddling him won't help him achieve that." He was so shocked that he didn't even notice Endeavor leave, and he went back to his own headquarters in a haze. His mind couldn't process what he just heard. He knew that Enji had ambitions, but he thought that he would act like how a hero should.

It was in his headquarters, around the evening, everything Enji ever said to him was going through his head like a broken record. Around the twentieth time he heard the word 'training' in regards to his sons, something clicked, and he realized that the 'training' Endeavor gave to his sons wasn't what he thought it was. He thought it was something they asked for, or maybe it was for self defense since it was dangerous being the child of such a popular hero. It wasn't. It was him trying to channel his own ambitions through them, with violence. He was overcome with rage, reminded of his own past, of how his father would hit him.

„Corrosive? Why is everything melting?" asked his student, Fumiko, who came from UA to do her work studies at him.

„I'm going to kill Endeavor." he said through gritted teeth, and while Fumiko wasn't sure what got him so worked up, she was sure that he meant it. She worked with Corrosive long enough to know that when he got angry, he did unreasonable things, unreasonable and dangerous things, all the while being terribly stubborn about it. She was sure that he would indeed do it, then have a breakdown afterward while being carried in an armored car towards Tartarus, and, she liked Corrosive. He was the only hero who didn't say that villains shouldn't be killed, who let her experiment with all the poisons she wanted, let her do things silently and efficiently. She was determined not to let him ruin his life. So she teleported near him, and injested him with her newest non-lethal poison. He quickly fell asleep, to shocked at Fumiko's sudden 'attack' to do anything against it.

He woke up two days later in his bed, not being able to move his body at all.

„Finally. I worried I put you in a coma or something." sighed Fumiko, who was sitting next to him. He wanted to speak, ask her about her betrayal, but she shut his already uncooperative mouth just with a simple look.

„You were about to do something very, very stupid." she started in a low voice, like talking to a child „Do you know what you would have caused? Killing Endeavor? You would have been sent to Tartarus for god's sake!" He was sure that the anger in his eyes could still be seen, his unsaid words clearly being heard: 'I won't let any child abuser live!' She sighed again, sometimes a conversation with him was like talking to a toddler.

„Try a different perspective then. What would have happened to me? I can teleport, maybe I got you there. Worked together with you, and bamm, I'm going to Tartarus too. It would be a great opportunity for everyone who doesn't like you to get rid of everything that is even slightly connected to you." it was only then that his actions hit him. No matter what, he didn't want to drag others into it. „And what about the villains? If you go away, you know they will become much braver. No matter how unknown you are, they feel that they can't just do anything." He sat in that bad for a long time, just thinking about everything Fumiko said. After what felt like hours, he could finally move his mouth again.

„I'm sorry. I just felt so bad, so guilty, like I could have done something, stopped him from going down that path. I thought that if I killed him, then went to Tartarus maybe I could atone for it." Fumiko was just looking at him, letting him take it at his own pace. „But, you're right. I can't do anything without sacrificing everything, so I promise I won't."

„Don't be so down. There are still a lot of villains out there waiting to be seen by you then never again, and maybe we can change his mind after a while."

„Maybe."

That conversation still replayed in his mind as he sat in his hospital bed after his fight with Stain. Maybe it was time to try and reconnect with Endeavor. Maybe he could change now. Maybe, they could even be friends again.

AN: It's a shorter chapter, but I'm pretty happy with it, the original chapter 21 which is now 22 is halfway done, so it should come sometime next week.

Some probably already saw, but I got distracted and started writing a new fic again, it's called 'Hemomancer', it's a PJO fanfic. Maybe check it out? I've uploaded two chapters, working on the third right now. Plus I'm already planning a sister-fic for it, similar to what 'A Broken World' is to this one.