Haru

Before he was a test subject, Haru had a very happy life with his mother, father and his twin sister Maki. They were all close and loved each other a lot, and he was especially close with Maki. He loved coloring, drawing and playing with her. The two of them would also save up on their allowance money and go spend it on miscellaneous trinkets at a nearby store right around the corner. Their elementary school was also relatively close, so they would walk there with each other as well.

When they were both 10 years old, Maki had to stay home sick with a cold, so Haru would end up walking to school by himself that day. Before leaving, he promised Maki to get her something from the store they always went to. Maki had lost a majority of her own hairclips including the two red ones she always wore, and he was planning to get her some new ones by the end of the day. However, he never did manage to give her those pins, and that's why he wears them himself.

Haru went to school and went on with his day normally. However, when his school day was coming to an end, back home human extremists had broken into their house and wound up killing both his parents and Maki. Shortly after, that's when the Hawk Party intervened upon being made aware of what was going on by killing them too.

By the time Haru arrived home with Maki's gift, he returned to multiple ambulances, police, and disguised hawks alongside the undisguised Hawks. The fact that humans were responsible for killing his family would be the basis to the experiments being done on him.

Assuming that the hawks have enough political influence to adopt children into their program, that is exactly what they did with Haru. Since he had no other family to go to, the Hawks adopted him instead, seeing research potential in him. Originally, he was not intended to be experimented on as heavily as he was. Nothing was being done to him about half a year or so into him being with the Hawks, but eventually there was open research about the effectiveness and relation of brainwashing to certain torture methods.

Haru was seen as a possible test subject to prove if this would end up an effective way to brainwash people, and the end goal would be, again, to brainwash him to have an extreme hatred towards humans. They did this by using his family, saying things like: Humans think they can go around and hurt us birds because they only care about their own well being. They don't care about us, or our families. Yours must've been terrified, right? If humans didn't exist then they would've still been alive. Without humans, there would be much less suffering in the world. Don't you want revenge? You don't want their deaths to be for nothing,right?

Including this, he would also be subject to various torture, especially mental torture. To keep him in line, they kept a gold collar around his neck that would detect intentional use of his vocal chords, and give him a rather strong shock whenever he spoke. Presently, he has wore this collar for about 4 years.

The brainwashing and torture proved to be successful, and Haru now carries intense hatred towards humans. With that success, the Hawks saw that as the potential of creating brainwashed soldiers, which would include children like Haru. Haru was then still undergoing the experiments, but around fourteen he began being trained excessively, for about as long as four or five hours a day. In order to keep up with the intense training, he would also be drugged to spike his energy and strength.

With his brainwashing and physical training proven to be successful, the Hawks would then "enroll" him as a student in St. Pigeonation right above the lab. He was enrolled when Hiyoko, the Human Representive, would also be enrolled. Doing this was supposed to be somewhat of a test run, as they wanted to monitor how Haru behaved around Hiyoko.