Leon Soryu's History
Season 2
Leon first appeared at Card Shop PSY, where he fought Daigo. Leon used Aqua Force and made cryptic references to feeling the wind, but nothing else about him was revealed.
He next appeared at the VF Circuit Hong Kong Stage, where he participated as the leader of Team Dreadnought, who fought Team Q4 in the finals of the stage and defeated them, and it was implied that the "wind" he referred to is actually PSY Qualia.
Note that Leon was the one who said the "wind" was PSY Qualia, though it's likely he was referring to a more metaphorical "wind", rather than the actual one that he summons, as even after he loses the Void's power, he still retains this supernatural ability to command the wind. While initially assumed to be a side effect of either his PSY Qualia or the Void's influence, it's more likely that it is unique to Leon himself. He seldom uses PSY Qualia beyond the events of season 2, but frequently creates small breezes, and even gusts, seemingly out of nowhere, at his discretion.
In episode 90, it was explained by Leon that his family once ruled the Seven Seas due to them having the power of Aqua Force to back them up. Then suddenly the Aqua Force disappeared causing the Soryu family to lose all their power over the seas, which lead to their being long forgotten. However Leon stated that the family foretold a prophecy that a child who would be "embraced by the wind" would restore the family name and the Aqua Force clan to their former glory. He solely believes that he is that child that the prophecy had foretold.
As the winners of the Hong Kong Stage, Team Dreadnought were invited to participate in the Final Stage. However, upon being transported to the space between Earth and Planet Cray, Leon and his team opposed the other teams. Leon revealed that he had made an agreement with Void to restore the Soryu clan to its former glory. He used Void's power to scatter the others and defeated Toshiki Kai, but Leon was defeated by Aichi Sendou. When Aichi turned the tide in the battle to save Cray from Void, Leon, who had been freed from Void's influence, helped him.
Season 3
He is seen again in Cardfight!! Vanguard: Season 3, and traveled to Japan to participate in the Vanguard Fight High School Circuit. He is seen cardfighting Asaka Narumi, and wins by break riding Last Card, Revonn.
Leon and his team later accept a challenge that was meant for Miyaji's Cardfight Club, and he cardfights Eru Nakagami. He defeats him and meets up with Takuto, Aichi and co. for friendly fights afterward.
He later meets Kenji Mitsusada and co., who challenged him to a cardfight, with Ali and Lee challenging Jillian and Sharlene as well. During the fight with Koutei, Sharlene and Jillian lose and get Reversed while Kenji manages to Superior Ride Dark Dimensional Robo, "Яeverse" Daiyusha. However, Leon manages to harness the power of the wind and win via Break Riding Blue Wave Dragon, Tetra-drive Dragon. It is interesting to note that despite Koutei's constant belittling of Leon, his family, and the Aqua Force in multiple attempts to discourage him, Leon isn't provoked. It is likely that Koutei in his Reversed state reminds Leon of how he was under the influence of Void, and as such, possibly makes him pity Koutei. They proceed to un-Reverse Yuri, Jillian, Sharlene, and Team S.I.T. Genius. He is seen leaving with the twins after the entire fiasco.
In the High School Circuit Finals, he is seen in the final match against Ren Suzugamori where he was overwhelmed by his Revenger, Raging Form Dragon. Afterwards, both discussed the Reverse phenomenon happening to other cardfighters.
When it becomes apparent that Takuto and Kai are the ones that he needed to defeat in order to save the reversed fighters, he arrives at Card Capital in order to see Aichi. He challenges Aichi to a cardfight but stops as soon as he rides Blaster Blade Liberator saying that his wind did not pick up upon riding his avatar meaning that Aichi has reservations about facing Kai stating that he shouldn't even try if he's in this state. Naoki, seeking a way to help Aichi in his own way, challenges Leon. Inspired by his motivation, he takes up Naoki's challenge and defeats him several times over. Though his enthusiasm was great, if Naoki were to follow Leon, he would just slow him down, instead stating that he is entrusting Aichi to Naoki Ishida.
Later, during a fight against a Reversed Fighter, Leon finds himself activating his PSY Qualia transporting him to where the normal Takuto is locked on Cray. Upon discovering who the fake Reverse Takuto is on Earth, he takes it upon himself to obtain a mirror to see Takuto and together storm the Tatsunagi Building with Sharlene and Jillian. Luckily, they were able to make it in time before Aichi became fully Reversed, allowing Takuto to assist Aichi in suppressing his Reverse with his PSY Qualia. With Aichi sidelined because of the strain of such an act, Leon decides to go in with only Takuto while Sharlene and Jillian stay behind with Aichi and the others, Sharlene giving him her compact mirror so he can see Takuto.
Upon seeing the Reversed Takuto, he is transported to another area to face off against a Reversed future self who surrendered to Link Joker complete with Blue Storm Karma Dragon, Maelstrom "Яeverse". This puts Leon in a situation where he had no field and no cards, but it was then when he realized that it was this kind of situation where his future self gave up hope and surrendered quietly. Through his bonds, he was able to face a near hopeless situation to Break Ride to Blue Wave Dragon, Tetra-drive Dragon, increasing his power and double critical triggered to end the game. Having defeated his Reversed self, Leon overcomes his karma (quite literally) and redeems himself for his sins in the Asia Circuit series. However, because Reversed Takuto used part of Leon to produce the "future" Leon, he became too tired to continue.
Season 4
In season 4, Leon agrees to train Naoki and the others on his island. However, Kai confronts him and quickly realizes that he remembers Aichi and says he has decided to wait before taking action. While training, he chooses to stop fighting Naoki until he reaches a small islet nearby. After Naoki and Kamui succeed in reaching the small islet, Naoki challenges Leon again with his new Brawler deck. However, he still loses but Leon says that is where his strength lies.
It's worth noting that while Ren inially feigned amnesia to abide Aichi's request, Leon made no such attempt, and readily agrees to Naoki's plea. This would suggest that Leon doesn't agree with Aichi's actions, and maybe even considers them foolhardy. There is also the possibility that Leon is even somewhat angered by Aichi's almost careless disregard for his friends and decision to stay alone, potentially viewing it as hypocritical, as it's a situation and frame of mind that Leon used to be in, and now realises is folly.
In episode 187, he and Ren came to the Sanctuary to aid Kai and Gaillard, but how they got there is unknown. They are there to witness Aichi's battle against Kai under the notion that if Kai lost, he, Naoki, and Ren would be made into the new Quartet Knights and protect Aichi until the end of times. During this batte, Kai points out that what he is doing is similar to what Kai was going to do after the previous Link Joker Invasion and that it's wrong, stating that if Aichi is going through all this pain that he would instead take it upon himself to seal himself away with everyone also agreeing to do so if they were in his position. At the end of the fight, the Link Joker seeds sprouts and attempts to take over Kai but Blaster Blade arrives and cuts the seed into many pieces that eventually find their way to other hosts including Leon. It is explained that the seeds will go to those who have the strength of love and forgiveness and that they will seek out others for all eternity, allowing Link Joker to slowly but surely be recognized as a clan of Cray. He, along with everyone else, then escapes the Moon Palace before it breaks down and returns to his normal life.
