He was the leader of Team Satisfaction, but was caught by Security. Blaming Yusei for that, Kiryuu died and became a Dark Signer to take revenge.
Kiryu came to Yusei, Jack, and Crow and formed Team Satisfaction with them because he believed that they may never be able to leave the Satellite so they would just have to be satisfied with what they had. As team Satisfaction, they went around Satellite defeating duel gangs to unite Satellite. As they went to face with the last of the duel gangs, one of the members tried to kill Yusei by pulling him off of a building but Kiryu saved his life and Jack took out the last member of the gang, thus uniting Satellite. However, as time passed, Kiryu just began going after anyone who simply had a duel disk and soon Crow and Jack left but Yusei stayed with him. Eventually, Kiryu comes to believe that the ultimate duel gang is Security and decides to go after them, and at this point Yusei leaves him too, because he thought that Kiryu wouldn't be crazy enough to go after Security on his own.
Kiryu became a Dark Signer and swore to kill Yusei for betraying him. He and Yusei meet in the Satellite and they begin to duel. Yusei notices he has a new deck and has completely changed. All the while Jack and Crow are watching the duel. During the duel, the reminisce about what happened before and Kiryu eventually brings out his ultimate monster - Earthbound God Ccapac Apu - and nearly wins the duel but Yusei's D-wheel breaks down before the attack connects, ending the duel. Kiryu then mocks Yusei and leaves. When he returns to the Dark Signer's hideout, Rudger asks him why he didn't finish Yusei off and Kiryu tells him that it doesn't matter because through the power of his Earthbound God, he knows that Yusei is afraid of him and as a result, he can defeat him anytime he wants to.
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