Kalin Kessler, known as Kyosuke Kiryu in the Japanese version, was a member of the Dark Signers and is currently a resident of Satisfaction Town.
During his time as a Dark Signer, Kalin wore the black robe of the Dark Signers accented with blue stripes. His dark mark was the Giant. He had extreme hatred towards Yusei Fudo and his previous team (The Enforcers), but later forgives them after finding out the truth from his loss to Yusei. He is brought back to life after Goodwin's defeat. He was last seen in Crash Town, where Kalin attempted suicide by dueling in order to atone for his wrongdoing, only to be forgiven for them by his former teammates, Yusei Fudo, Jack Atlas and Crow Hogan. He later stays behind to help rebuild the town along with West and Nico, later renamed Satisfaction Town to cherish his team's honour.
Originally, Kalin started as a cheerful and good person, looking out for his teammates and giving hope to them. But after his team conquered the entire city of Satellite, Kalin became obsessed with protecting what they worked so hard to obtain, growing paranoid into believing that any duel gangs not under his control were a threat to the order they brought. This caused him to begin dueling people recklessly including kids, harming them in the process, which eventually lead him to challenge the city's security, causing his downfall, being captured by them and sent to prison to die blaming Yusei for his capture.
As a Dark Signer his personality has become more crazed, bursting out in insane laughter at his opponents and enemies' pain and misery. He also showed great hatred towards his former teammates, Jack Atlas, Crow Hogan, and especially Yusei Fudo, to whom he would often call a traitor and exclaim "You betrayed me!"
After his death and revival he came to realize that all his pain came from his own mistakes, regretting what he has done in the past. Depressed and guilty he ventured to Crash Town looking for a place to die, uncaring of what befalls him. His method of dueling shows that as his monster's effects act like Russian Roulette. But after seeing Yusei and the kids, West and Nico attempting to save him, Kalin regained his self-worth and kindness as he vowed to protect them and all the citizens of Crash Town.
When a Dark Signer, Kalin was able to project his Earthbound Immortal into fog as a purple image, which also caused Yusei's mark to react. Even after being revived as a normal person again, he was still capable of inflicting real damage to an extent, as his "Infernity Des Gunman"s attack was strong enough to fully knock out Lotten.
Kalin was once the leader of The Enforcers (Team Satisfaction in the original version), consisting of himself, Yusei Fudo, Crow Hogan and Jack Atlas. He met with the trio for the first time when he approached them with the idea of the Team. He fought for his own ideals and unique sense of unity and gave his team a true glimpse of hope under the despairing circumstances of Satellite.
The team managed to conquer all the team areas in the Satellite. During the face-off with the final gang, one of them almost kills Yusei by pushing him off the roof, but Kalin saves him.
After conquering all the zones in Satellite, Kalin got into a fight with a kid from Team Insect, something that prompted Crow and Jack to go against Kalin and leave the team. Later, when Sector Security began arresting duelists in Satellite, Kalin decided to take action into his own hands and blows up a part of the Security base, and he seemed happy that he did it. At this point, Yusei leaves as well. The abandonment felt at the Enforcers' dissolution causes Kalin to become obsessed with ruling Satellite forever and reuniting his group for their last Duel against Security. He is eventually pursued by Security until his former teammates come to his rescue. However, neither Crow, Jack or Yusei believe they can defeat Security, so Kalin confronts a Security guard on a Duel Runner and ends up driving through a bunch of crates, severely injuring the guard. Before he could finish him off, Yusei interfered and isolated him in a room. Yusei then decided to call himself the leader of the Enforcers in hopes that they wouldn't arrest Kalin. But security found Kalin and arrest him for injuring a Security. One of the Security members already figured out that Kalin was the leader and Yusei tries to convince that he is the Enforcer's leader; Kalin sees Yusei trying to convince Security to let Kalin go, and he mistakenly believes that Yusei had him arrested purposely. Kalin attempts to fight him but is held back by Security and is arrested.
In the facility, Kalin was painfully imprinted with a criminal mark, and the prison guards constantly beat him up and intentionally withheld his food rations. Although he claimed that he could survive the abuse, his resistance was weakened when Security took his Deck, which was his most prized possession. After that, Kalin is seen in a cell, near death from starvation, when a voice spoke to him. It calls itself an "Envoy from the Underworld" who came with a proposition. If Kalin has some sort of unfinished business that he could come back to complete it as a Dark Signer. Because of his grudge against Yusei and his wish to fight the last battle with Team Satisfaction, Kalin accepts, dying of starvation and being reborn as a Dark Signer. At some point after that, he escaped prison and eventually joined up with the other 3 Dark Signers, under Roman's leadership.
Kalin was waiting for Yusei who had been accompanied by Crow, and as they both enter the B.A.D. area, Yusei and Crow are both shocked to see him. He jumps on his Duel Runner creating a shadow barrier in the process, which suddenly forms, separating Crow and Yusei. The barrier began to take the shape of his mark, the Giant. Kalin then exclaims that he will take down Yusei, as their Shadow Turbo Duel is about to begin.
Before the Duel starts, Jack appears in a helicopter, Kalin exclaims that the Enforcers are together again. The Duel begins with him gaining total control and telling Yusei to suffer. Throughout the whole duel, Kalin laughs hysterically when referencing their past together. Yusei pleads with Kalin to stop, reminding Kalin how he saved Yusei's life long ago. Yusei still doesn't understand why Kalin hates him. Then after Kalin's direct attack, he remembers. Yusei had stopped Kalin from escaping arrest after he almost killed one of the Sector Security squad members. Yusei Summons "Stardust Dragon", but Kalin counters by Summoning his Earthbound Immortal "Ccapac Apu", which nearly ends the Duel. However, before he could claim victory, Yusei's Duel Runner malfunctions, critically injuring Yusei. Upon seeing this, Kalin laughs and ends the duel without a victory, telling Yusei to suffer the same pain that he endured.
When he returns to the headquarters of the Dark Signers, Roman Goodwin asks him why he did not kill Yusei. Kalin replies that he will do so if all Dark Signers are present. He also says that he will let Yusei live in fear after witnessing the power of his Earthbound Immortal.
He is present along with the rest of the Dark Signers when they all confront the Signers right after Yusei's and Roman's duel concludes. He tries to degrade Yusei by calling him weak, however Yusei's opposite reaction to that comment surprises him.
After Yusei finally arrives to the Giant tower, he and Kalin began their rematch telling him that this will be the Enforcers' last duel. He continues to use his Handless Combo strategy. He eventually Summons his Dark Synchro Monster "Hundred Eyes Dragon" once again and assaults Yusei with its effect. After Yusei destroys it, Kalin reveals to him the horrible incidents that occurred to him while being a prisoner before becoming a Dark Signer.
As Kalin says to Yusei that by accepting his fate, he can return to show Yusei the fear he felt at that time. Intending to do this through his Earthbound Immortal card, he then summons "Ccapac Apu" once again trying to finally defeat Yusei with it. However as Yusei manages to fend off the Earthbound Immortal's assault, the Immortal itself begins to trash the ground where the Duel is taking place. As Kalin began to have some difficulties with this, Yusei extends his hand to offer his help, symbolizing the occasion where Kalin risked his life to save Yusei. However, Kalin rejects it, stating that it's too late and that it is completely pointless. After this, once Yusei Summons "Majestic Star Dragon", it ultimately takes down "Ccapac Apu".
By this, Kalin loses and in the end not only does he make peace with him, but also reveals to Yusei he had another purpose besides that of revenge when he transformed into a Dark Signer; Kalin also wanted to carry out the Enforcers' Last Duel. Following that, Kalin finally turns into dust.
Kalin is the third Dark Signer to be defeated.
When Rex Goodwin is defeated in the final battle, and the King of the Netherworld is destroyed, Kalin is restored to life, along with the other Dark Signers except for Roman and Goodwin himself.
After these events, he is said to have gone on a trip, according to Luna.
Following the events of the Dark Signers, Kalin resides in a town that is ruled by dueling. His appearance has gradually changed over the course of time; his hair is much longer than before and he wears a coat. He also carries around a harmonica around his neck (which he plays often) and his personality shows no emotion; when he does show any emotion it is of sadness, concern, or pity. He follows the gang leader Radley, and a bunch of duelists that dominate part of Crash Town. Barbara tells Yusei that Kalin came to this town to die. Kalin says he has forgotten the meaning of words such as satisfaction. He duels one of the members of another gang led by Malcolm and ultimately wins against his opponent. After the Duel, Yusei tries to talk to him, but he gives no reply as he rides off with Radley's gang.
After the duel Kalin is in the gang bar, but leaves so he can be alone. Kalin still has memories of the time when he was a Dark Signer (how this occurred is unknown; it is possible that he remembered because he became a Dark Signer willingly, like Rex and Roman Goodwin, and that unwilling transformations like Carly's result in a loss of memory). Being left with the guilt from what he had done to hurt his friends, he now struggles to end his life through the only thing that once mattered to him: dueling. The next day Kalin challenges Yusei and reveals his intentions, pleading Yusei to defeat him so that he can die in the mountain. Kalin fights hard, refusing to simply throw the duel, even resorting to summoning his "Infernity Doom Dragon". Ultimately, however, he is defeated by "Stardust Dragon" again.
After the duel Yusei and Kalin are double-crossed by Barbara, who was secretly a member of Malcolm's gang, apprehended by the undertakers and taken to the mountains along with Radley after losing to Lawton, Malcolm's brother. Kalin gets to work with no second thought; even Yusei couldn't convince him to escape otherwise. Yusei then punches him in the stomach leaving him unconscious he takes Kalin and escapes, as they escape they run into Nico and West. Soon after Lawton and Malcom's gang members find them, Yusei goes and turbo duels Lawton, while Kalin is running away with Nico and West in a miner cart from Malcom's gang members. Kalin manages to steal a Duel Runner from one of the members of the Malcom gang, using it to get to the duel between Lawton and Yusei. In an attempt to get rid of them, Lawton throws dynamite at them, causing the mine to collapse and leaving Kalin and Yusei in a crevice, while West and Nico were taken as hostages by Lawton. After visiting the graves of those who went to the mountain, Kalin vows to fight for those either still working in the mountain or lost their lives because of it and to save West and Nico, calling himself a "Death God". Returning to Crash Town, to the shock of Lawton and the others, he and Yusei engage in a 2 vs 1 Duel with Lawton, to free the town from his horrid rule. Though their duel was coming to an end Lawton's men interrupted and proceeded in stopping Yusei and Kalin. But the members have a change of heart and decide to hold back. Lawton and Barbara attempt to make a final getaway but are stopped by Crow and Jack. In one last attempt Lawton detonates explosives in the city, creating a diversion. Kalin gives a chase on Yusei's Duel Runner and catches him in order to finish his last turn. Lawton, knowing his top card is a spell card that would render Kalin's "Infernity Des Gunman" useless, and agrees to finish the Duel. But Kalin uses the effect of "Infernity Climber" to draw this card instead of his spell card, using Des Gunman's effect, finishing off Lawton. After that Kalin stays in town to watch over its reconstruction, and watch over the kids, West and Nico. In honor of his team he named the previously known Crash Town, Satisfaction Town.
In episode 150, he's cheering on Yusei. Two episodes later, Kalin reappears and is seen being defeated by Jack in Satisfaction Town as Jack was self-training himself to once again regain his crown as the King of Riding Duels. Kalin tells Jack that he has become a lot stronger since the days of the Enforcers but he's still not satisfied, to which Jack agrees with.
To unlock Enforcer Kalin's story, Activate the PSP Recognition and insert Yu-Gi-Oh! GX Tag Force 3. Next, take Kalin to see Lenny at the shoreline and select the option "Look at partner in a new light". Kalin will appear during the daytime.
Dark Signer Kalin Story
Kalin appears at the Player's house and tells him they will eliminate the Signers.
In the first event the Player and Kalin encounter Crow and Rally Dawson and they challenge them to a Tag Duel to eliminate them, though he is not a Signer.
In the second event Kalin lures in Jack and Luna into a trap and challenges them to a Tag Duel with Leo watching them.
In the third event Kalin and the Player encounter Yusei and Akiza Izinski and challenge them to a Tag Duel.
In the final event, to the Player's surprise, Kalin challenges him to a duel.
In the end, Kalin has peace of mind that his friends have grown stronger, reveals he did not succumb to the darkness inside him and is thankful for one last duel. A photo of him, the Player, Crow, Jack and Yusei falls out of his pocket.
Upon completing the story, the Player receives three copies of Earthbound Immortal Ccapac Apu and two personal photos: The first is "Kalin Kessler - Last Duel" and the second is "Kalin Kessler - The Enforcers".