Kyojin has not actually killed anyone, he has on occasion caused significant bodily harm but he does not have a body count.
(To clarify, Kyojin has had no training whatsoever and as a result doesn't use weapons, everything that he has achieved has been a direct result of Kokatsu's planning, his sheer survivability and an absurd amount of luck and Molotov cocktails)
(I didn't know badgers lived in packs before this)
(I have no clue how feral children are supposed to act
Age:0-7
Little to nothing is known about Kyojin's parents, or his life before the forest, or even how or when exactly he ended up in the forest to begin with, what is known is as follows:
The animal control worker that "found"(tranqed) him referred to him as Kyojin when giving him the police, at the time it was assumed to be his name but it was later discovered that it meant "lunatic".
When informed of this Kyojin didn't stop laughing for half an hour.
It is assumed that he was between the ages of 4 and 5 when he began living in the forest.
During his time in the forest he was raised by what seems to have been some form of badger however at present this cannot be confirmed as we have been unable to find anything that even remotely resembles a badger within 5 miles of where Kyojin was found
Kyojin was 7 years of age at the time of his (what's the proper term for tranqing the shit out of a feral child and taking them to the cops?) "Reintroduction to society" when he awoke it was quickly discovered that he was quite fluent in the English language for his age and situation and he quickly demonstrated his fluency by screaming an alarming number of curse words at everyone in earshot
After he had calmed down
(was mildly sedated after he bit an officer)
a psychologist that specialized in dealing with extremely aggressive/traumatized children was called in and eventually (After the drugs wore off and Kyojin had been bribed with food) was able to convince Kyojin to stop trying to escape/kill everyone
Eventually after around a month of bi-weekly
visits Kyojin was deemed mentally sound and fit to be placed into the foster care system.
It is assumed that either the psychologist was incompetent, or Kyojin is far more skilled in deception than we previously thought.
Age:7-13
Over the next 6 years of his life Kyojin was alarmingly low profile given what we now know, he seemed to have perfectly reintegrated into society, having average grades in school and a solid friend group
(it was later discovered that Kyojin had "forcibly adopted" these friends after he caught some older students trying to bully them, said students were later admitted to a local hospital but at the time refused to say what caused their injuries) but then at age 13 circumstances forced him to move to another foster home, this is where he met Okibo.
Age13-17
After meeting Okibo Kyojin went from slightly feral to absolutely f*cking insane.
A week after meeting Okibo there was a school field trip to a zoo, on this field trip Kyojin managed to:
(After sneaking off and putting on a mask)
Jump into a lion enclosure, steal the Lions food (he threw it at a classmate), fight and Win against an adult lion while unarmed and he then rode said lion on a five hour rampage throughout the zoo during which he freed half of the animals in the zoo and caused $346,000 worth of property damage, the rampage ended after he was tranquilized by zoo staff (they were aiming at the lion) and the only reason that he escaped from the zoo without being arrested was because he wore a mask and Okibo managed to sneak back in and drag his a*s out before the cops got his mask off.
That was just the first week.
The following years followed a similar pattern with Kyojin accompanying Okibo on his vigilante work and Okibo dragging Kyojin's a*s out of the fire whenever he decided to go on a tear and wreak havoc.
For the most part it was just random chaos,
Okibo would just wander around town until he found a target and whenever Kyojin decided to tear sh*t up he never spent more than 30 seconds planning.
And then they met Kokatsu.
It was Okibo that met her first which was surprising on it's own not to mention that she was at their foster home to recruit people to help her commit arson.
Needless to say they got along Very well.
Age 18
Kyojin hangs out with Kokatsu for her birthday, talks to God and eats a banana.
Personality:
Pack Mentality: Kyojin might have only spent a few years with the badgers but those years have taught him 2 lessons:
1:protect your family to the death.
2:when in a fight, go for the groin.
Demigod of Chaos:(not literally but he acts like it)
Over the years one thing has always been clear about Kyojin, he is a force of anarchy.
Since he met Okibo he has caused 7 zoos, 5 schools and a bakery to shut down.
Since he has met Kokatsu he has caused 6 companies and 9 criminal organizations to be shut down/arrested, on several occasions has had to flee from SWAT teams and there is a standing $500,000 bounty for his death under the alias of Havoc.
He does not do this because he considers it the "right" thing to do, he does it because he finds it amusing and because Kokatsu said to.
Eldritch Badger:
Kyojin spent several years living with badgers, as a result he's developed a mindset of
"I will not die, and if I do I'm gonna drag you down to hell with me", combine that with the fact that he's just naturally as hard to kill as a cockroach and the end result is that he has survived situations he had no right to survive, for example:
Having a criminal organisation collapse a building on top of him.
Having an Extremely paranoid baker pull out an LMG and empty the clip at him when he tried to steal a cake at 3am.
Having a SWAT team raid an apartment building that he was storing things in and having to throw himself out of a 7th story window to escape
(To summarize, Kyojin typically acts as a comedic relief, planning pranks or just being chaotic in his off time, but when he starts taking things seriously he can be terrifying)