Khun Aguero Agnis/History

Background
Not much of Koon's history is known, other than the fact he was once a member of the Koon Family.

When he was 10 years old, he took part in the yearly "official fights" where its participants are 10 year old children from the Koon branch families. The fights are inhuman and bloody and he emerged as one of the winners. As a winner, he was allowed to wear the crest of the Koon Family while the losers were abandoned.

He was later expelled from the Koon Family, due to the failure of his older sister to become a  Princess of Zahard.

At one point his attention was captivated by Maria]}, who was kind and altruistic, things that seemed surreal and incomprehensible to him. He felt she deserved the power and prestige of a princess, and manipulated events to make her a princess by usurping his own sister. However, ever since then he felt lonely, and didn't know that he felt lonely until he saw [[Baam's resolve to go up with Rachel.

After his expulsion, he was sent to the Floor of Test as a regular. Before this happened, he raided  his dad's treasure hoard and stole equipment.

Evankhell's Hell
Koon began on the Second Floor with the other Regulars. Ever since the beginning he displayed his natural genius and cunning, and from game one, thought several steps ahead of the other Regulars. He found a few allies during the first test and stored them in his briefcase. He ran into a large red Regular, and asked him if he wanted to become an ally. The Regular remarked that trying to find allies was stupid as the test was all about killing each other, to which Koon replied that finding allies was important, and was part of the "mindset of a ruler". He stated that the Regular was not even fit to be ruled, and promptly defeated him. He then encountered Baam, and once seeing the Black March in Baam's hands, he takes interest in him. Then they prepared to move on, until they were attacked by Rak. He and Baam hid behind a rock from Rak while trying to decide what to do about their situation. He noticed that Baam had the  Black March, and decided that if Baam possessed such a weapon he was probably special and could make a useful ally. He introduced himself to Baam while Rak continued to rage at them on the other side of the rock. It was then announced that they had to create a team of three, and he and Baam were left with no option other than to grab Rak, which upon failing to secure his cooperation, they did. Paired with Rak and Baam, Koon managed to get through the barrier test easily.

Yu Han Sung's Examination
Koon, naturally being a machinated thinker, tried to piece together the clues given by the sounds of previous test-takers and the time given before each reaction. Although Mr. Neonbag gave his team a useful clue, Koon half used it, and had already figured out the inevitable answer. But, wanting everything in he world to be dictated by logic, he refused to accept this, and tried desperately to figure out his own way during the test. Just before the time almost ran out, Rak kicked a door open and stated; where logic is not applicable, you gamble. Koon began to deny the test's mechanisms after Yu Han Sung's explanation, however, Yu Han Sung chastises him and exposes Koon's one weak point: He didn't trust anybody but himself. Sung then continues to note metaphorically to Koon that he knew what Koon was planning with the use of his suitcase, to Koon's disregard.

Crown Game
He played the Crown Game with his team, he and Rak easily demolished most of the other teams using their fighting skills. Koon was able to sucessfully trick his opponents by cloning the crown, and keeping the original in his suitcase,  Manbarondenna. He took a break in the middle of the game, and let the allies he had been storing in the suitcase loose to fight for them. The later opponents were more skilled, but Koon and Rak held their own. However, they lost the test when Baam jumped off the throne.

Position Test
Koon was then assigned the Light Bearer position and seeded first. He did well in the classes (although he commented that they were boring), and with Baam's help managed to collect a list of "friends". At first he was amused by Baam's determination to even help his enemies, but then made it clear to him that in order to follow Rachel, he would have to fail other regulars. He was then alerted to Ho's enmity towards Baam by Hwa-Ryun, and got Full to keep an eye on Ho. The night before the test Full told Koon that Ho acted strangely, and Koon snuck into Ho's room, and learnt about Ho wanting to kill Baam. He then started formulating a plan to save Baam...

Hide and Seek
Koon placed on Team A for the  Hide and Seek game. He masterminded the whole team expertly in an attempt to capture Quant, but the attempt failed making Quant feel overconfident, just as Koon wanted. He then moved to the second part of his plan to help his team's  It escape. He confronted Quant, and tried to make him think that Anak was in his briefcase, while really she was riding one of his lighthouses. Quant figured this out and tried to foil the plan by pushing Koon off the bridge, but it was then revealed that Koon had planned for that as well and had set up a pulley system attached to the lighthouse Anak was on. Anak was carried up to the exit while Koon was saved. However afterwards Laure, under Koon's command, blasted Quant up to Anak, and he was able to catch her.

After the Hide and Seek game, Koon appeared to lament his failure with his team, but it was then revealed that he was actually planning to get his list of "friends" through the test, and that he had made a deal to help Quant catch Anak, in order to facilitate things for his "friends" on the other team.

Submerged Fish
Afterwards, he submitted evidence to Lero-Ro proving that a  Ranker had intervened in the previous test, so that Rachel could proceed despite being injured. He revealed how he had used Quant to prevent Ho from murdering Rachel. However, when Rachel was "crippled" by the attack, he lamented his failure, even though his plan had actually saved her life. Afterwards, he discovers Rak's predicament at the hands of Yu Han Sung, and after laughing, he talks about his plot to put Maria on the throne. After listening, Rak sneers at Koon, saying that he's lost his resolve. Later, Baam asks the two of them if they could help him find a way to take the 'injured' Rachel up the tower. When Koon saw how Baam intended to go with Rachel, and how he asked Koon and Rak to go with him, Koon finally realized that his mistake back then was that he never asked Maria to go together. This realization inspired him, and he helped Baam gather teammates to help Rachel pass.

Last Examination
In the Submerged Fish Test, he masterminded the team to destroy most of the threats. During the test he felt something was suspicious with the setup. However, he was unable to stop Baam from "dying", and as a result of this felt guilty and decided to assist Rachel on her quest for the stars. It is implied he suspects Rachel's involvement with Baam's "demise".

Completing Fences
In a spoiler posted by SIU, Koon confessed to  Leesoo that he felt great sadness over Baam's death. He suspected foul play during the Submerged Fish Hunt and now wishes to avenge Baam, stating that the others were tools for this purpose. He splits the group into two:  one to climb quickly and attract attention and  one to follow safely in their wake. The spoiler ends with Koon wondering why only Baam was targeted and not Rachel.

In Part II, Koon seems to be called A.A (Agero Agnis). Whether that is his alias, new name or nickname is yet unknown. It is most likely he has cast off his name of Koon, similar to Hachuling. He is seen sitting on a chair in a throne-like manner, and is wearing summer clothes and a sun-hat.

He waits in a cafe for a scout named Edin Dan whom he wishes to recruit due to his skills. The scout is resistant until Koon makes a bet with him. Dan loses the bet and Koon carries his unconscious body to his base of operations. He goes to see Rachel.

It is revealed that he is aware that Rachel tricked him, and he shares the info with Ship Leesoo.

In shorter words, he is portrayed his team members to be ruthless when angered and can actually follow through on seemingly impossible threats or concepts of punishment.

After his team has decided their rankings, he tells them to be kind to and help Rachel, but never to think of her as a friend. He then tells them to despise her, because "She is the woman who killed my most precious friend".

It is then revealed that he climbs The Tower to surpass Koon Eduan and become the Koon Family's leader. Using that power, he states he will avenge his most precious friend, Baam.

Epilogue, Path
Koon informed Leesoo that he was at the 29th floor, and he was eager to meet up.

Connection
Koon and his team take the 29F test. Dan uses a talking bot on his phone to help him figure out where the enemy team is and brings Ran there to fight them. Though shaky at first, this ultimately helps the team win the Advance Battle. Koon is angry at Dan for using such unreliable methods and confiscates Dan's phone. Curious about the program, he types in "Twenty-fifth Night." Emile replies, "He's alive." Koon asks where he is and Emile responds that she doesn't know. Koon is disappointed but further questions the AI bot. He reasons that no one on Leesoo's team would do something like this and begins to suspect something. Apple interrupts him with the message that she has found "The Devil of the Right Hand." Koon decides they should capture him. He takes Ran and Novick with him to Cassano's hiding spot.

Devil of the Right Arm
He, Novick and Ran arrive at The Hand of Arlen. He deduces that the picture found by Apple was meant as a message for someone, and informs his teammates that they may encounter someone else. He uses his Lighthouse to guide them through the traps, but when Ran destroys the lighthouse, he is left with nothing to do. After being informed that he was "caught in a trap" by his own lighthouse, Koon is shot by a poison dart, but is protected by an Armor Inventory hidden under his cloak. When the assasin emerges, Koon waits until he comes close, then grabs him, stabs him, and forces him to describe who had hired him before killing him. Then he back-tracks the message on his lighthouse ("caught in a trap") and realises that it was his scout/lightbearer Apple who's sent them into this trap. As he runs into the Hand, he confronts the new slayer candidate, not knowing it was Baam, and is told by  Xia Xia that FUG orchestrated all the events leading up to this stage for the sole reason of killing him. The validity of this claim is low and should not be taken at face value. The new slayer candidate affirms Xia Xia's story, but Koon can immdiately see that Viole was letting them go on purpose. While the hand was destroyed begins to suspect that Viole is Baam.

Bet
After the hand is destroyed, he is found in the rubble by the Team Tangsooyook who followed the signal of Viole's pocket. Unconscious, he wonders if Jyu Viole Grace really was Baam when he was woken by the acupuncture needle in him being set on fire by Yihwa. Whether she was exaggerating about the power of her flames or Koon was simply strong, he easily put out the flame and was about to kill Wangnan. After everything was explained, he took them to his personal bunker where he found Gyetang dead and Dan alive but disabled. He goes up to the roof and comes to the conclusion that Baam really was the slayer candidate from the A-grade pocket he had when his speculations were confirmed by Hwa Ryun. After learning that Hwa-Ryun was working for FUG, and that it was she who faked Baam's death, he tries to attack her but is easily blocked. He is then told to enter the Workshop Battle, since the elders had agreed to let the winners become Viole's teammates. He goes down to tell Dan that he won't be able to run anymore, only to find that Dan hadn't been defeated, and still wanted to participate. Koon agrees and, after reaching an agreement with Wangnan, the two teams join forces for the upcoming tournament. He spends the next month training Team Tangsooyook for the 29F test, despite being exasperated by their immaturity.

Workshop Battle
Team Tangsooyook arrive to the 30th Floor and book rooms in a hotel, waiting to board the Archimedes. Wangnan, Dan, and Koon are watching TV in Koon's room while the rest of the team go sightseeing. While separated, the preliminary battle, One Shot One Opportunity, starts.

One Shot One Opportunity
Koon tricks Wangnan into thinking that he was betraying him in order to throw the two approaching enemies off guard. He then convinces Wangnan to run straight to where the rest of their teammates were trapped, arriving just in time to save them from Chang. Chang is surprised to see Koon alive. Koon threatens Chang, implying that he was the reason why Chang had that scar over his right eye. Chang and Quatro are sent up by Koon, with Chang giving Koon the middle finger. Koon convices the team to leave Prince and Miseng, arguing that it would be too dangerous for the rest of the team to save them. After the rest are sent up, Wangnan suddenly refuses to leave them behind and that he'd rather die. Koon locates their missing teammates but refuses to do more than that. He quickly changes his mind once he realises that the person holding Miseng and Prince captive was Verdi, a puppetmaster in Leesoo's team. He rushes to save Viole once he realises the danger he's in and tells Wangnan to kill Verdi. Along the way he sees Horyang, who he directs him to Wangnan. He then proceeds to the FUG residence, watching Viole and Ship's team battle, with a sorrowful expression settling on his face when Viole says that he had already lost the will to live, not noticing that he was being watched by Rak, who approaches them when he returns to Wangnan, to send both of them on the Archimedes.

Archimedes
Back in their room, Koon asks Rak how he knew he was alive, to which he replies that Hwa Ryun told him everything, even that Baam was still alive. He is beaten by Rak and is called a coward for doing nothing to save Baam. Afterwards, when Rak meets him on the balcony, telling him how happy he was that thy're both alive, wishing nothing more than to climb the Tower with him and Baam. Koon tells him, that they'll get Baam back in a way more ruthless than [FUG]].

Battle x Gamble
During the Workshop battle he disguises himself as Mr. Mask to hide his identity. Koon's chosen as one of the 10 gamblers of the "Plug test". During the first round, he's surprised and worried by the sight of the manipulated Miseng. Afterwards, during the round in which Goseng's participating, he bet on her even though the others wouldn't, due to her looking weak. Before the last round started, he's tied at first place with Reflejo. In the last battle, he bet all on Ran, who was winning as he expected. But due to unforseen consequences, both regulars were disqualified, leaving him in a predicament.

The Truth
He attended the meeting with the other gamblers, while the party was taking place. Koon told Io that the last bet should've been invalid, because the two participants were interrupted by a third party. After hearing the rules of the Development Tournament, he summarizes them for members of his team and appoints Wangnan as "Vanguard".

Koon Aguero Agnis/Historia