One of the earliest speculations regarding Vanguard's second season is that it is an alternate universe to the "main" timeline presented by season 1. This theory provides for the possibility that the characters in season 2 have not just had their memories altered, but in fact are remembering actual events that did take place. Advocates of this theory will generally agree that the Aichi we see throughout season 2 is still the same Aichi from season 1, and therefore not from the Asia Circuit timeline.
Spoiler warning: Season 1 and Asia Circuit details follow.
Outline of the Theory
This theory states that at the beginning of ride 66, Tatsunagi Takuto made an altercation to the timeline during his fight with Kai Toshiki, changing history so that Kai has always used a Narukami deck instead of a Kagerou one. Rather than "erasing" the past however, this constructs a new past that branches off from the old one. If this were the case, the exact timeline branch would have to have taken place at least two years ago (one year before the year that season 1 covered) as that is the first time that Kai is known to use a Kagerou deck, just as he encounters Ren.
In the new timeline, Takuto did not fight Kai, as he already had a Narukami deck exactly as Tatsunagi desired. Takuto instead met up with Aichi at Card Capital, and made an additional change by modifying history further so that Sendou would never use the Royal or Shadow Paladins. In their place, Takuto inserted his own Gold Paladin composite clan. If the alternate timeline theory is true, then the timeline now branches off from the main one five years in the past, when Kai first gave Aichi his Blaster Blade.
- Takuto's disappearances. After his fight with Kai, Takuto has seemingly disappeared and Kai does not recall fighting him. The alternate timeline theory provides that the actual point in the branch is two years ago--as such, if Takuto were to make the change two years in the past, he would never need to confront Kai Toshiki in the present of this timeline. Hence, in the Asia Circuit timeline, their meeting did not actually take place, and Takuto is not at the table. He never "disappeared"--because the changes he intended to make had already taken place, Takuto did not face Toshiki that day, and instead sought out Aichi. He later pulled the same "disappearing" act on Aichi, this time never leaving his office in Singapore. Takuto would go on to announce the VF Circuit the next day. It would be otherwise improbable for Tatsunagi to be able to travel to Japan by plane, have two cardfights at two separate locations, then travel back to Singapore to announce the Circuit in an afternoon broadcast within a span of approximately 36 hours. (Note that a flight between the two countries takes around 7 hours.) When Aichi and company left for Singapore by plane in the morning, by the time they arrived it was only a few hours shy of dusk.
- Fallible memory loss. Shin, Misaki, Izaki, Morikawa, Miwa, Kai, Kamui and Kourin do not recall Aichi having used the Royal Paladins. If their memories were merely modified, then their version of events could be disproven by viewing reruns or online recordings of the televised broadcast of Aichi's fight with Ren. We know for certain that these broadcasts are rerun after their original air date, because in ride 41's flashback Kyou watched a rerun of Ren's speech following his final match at the first national competition--during a total downpour in the dead of night. That speech was given in the daylight hours during fair weather, meaning it was not a live broadcast that Kyou was viewing. Furthermore, it was mentioned in ride 26 that there are Vanguard magazines which talk about pro cardfighters like AL4's lineup, and these would presumably talk about those fighters' clans and signature cards as well. If the modifications were simple memory rewrites, Aichi could make his case through a multitude of video and print media readily available to him. Some of it would even be stocked on Card Capital's shelves, within arms' reach. As an extension of this, if Takuto were to modify the memories of those associated with Team Q4, he would also have to modify the memories of every Vanguard fan and viewer across Japan who watched any of the national cardfights.
- Kai remembers limit break. He used his Narukami cards flawlessly in ride 68, showing complete knowledge of their skills and how to make use of Dragonic Kaiser Vermillion's limit break counterblast. This would suggest that he has used the cards at least as long as he had done so with his Kagerou deck. Toshiki shows none of the problems that Aichi has with using his own new deck.
- Except for Aichi, none of Team Q4 remembers PSY. When entering the card shop PSY in ride 69, Kamui and Misaki behave as if they had never seen it before, and Aichi is the only person to specifically recall having been there. Misaki says that she's interested in checking out other card shops, something that she had already done with PSY on Shin's orders in ride 23. Conspicuously, Aichi is the only character to address the Ultra-Rare members by name, and Rekka introduces herself to Misaki when Tokura should already know the girl's name from ride 45. There are problems with Takuto attempting to modify these specific memories; the least of it being that Suiko herself would be, as is explained in depth further on, immune to his memory modifications. Unless the two are directly working together, her unmodified memory is inherently dangerous to him. Since this shop was where Misaki first noticed Aichi's Qualia hurting him, if she did not remember PSY, then she would be unable to report these early symptoms to Kai in ride 40. If Kai did not get these early warning signs, he never would have left Q4. The false memories create a hole in the characters' lives that they should be fully able to notice.
- Kourin does not recall the Royal Paladins. As far as has been shown, Takuto can only achieve his goals through a direct cardfight with his target. Aichi and Kai's decks had to be replaced through a face-to-face confrontation with them. If he could simply replace Kourin's deck without her noticing, then it would be a contradiction that he could not do the same with Aichi and Kai. If however, the Royal Paladins never existed because of a branching timeline, then Kourin never would have wielded them in the first place.
- Kai remembers Blaster Blade. In ride 68 he can tell that something is wrong with Aichi's deck, and his memories of Aichi's Blaster Blade ride attempt to resurface. However, there are alternate explanations in that the new timeline cannot resolve itself properly without Kai giving Blaster Blade to Aichi. Thus, Toshiki is a walking paradox--he gives Aichi a card that sets off the events of season 1, and so no version of the timeline can exist without that moment, but the card itself and as a result that moment do not exist in the Asia Circuit timeline. This leads to a "yes and no" scenario where the moment must have happened, creating his memories of it, but it is impossible for it to have taken place, at the same time excluding his memories.
- Kamui does not remember limit break. In ride 69 Kamui and Team Handsome are shocked when Garmore's limit break activates and gives him an additional power boost. On the other hand, this may be countered by the possibility that it was not limit break they were shocked at, but Garmore's limit break. It is entirely possible that the group had never seen Garmore before, and so he did not know that it possessed a limit break despite knowing what limit break is in the new timeline. Ergo, Kamui was not expecting it.
- Kamui remembers the Royal Paladins. During their cardfight in ride 69, Kamui recognizes that something is wrong with Aichi's deck. He cannot however, recall exactly what went wrong.
- Because the theory provides that Takuto was able to be in "two places at once," by modifying the timeline in his fight with Kai and then meeting Aichi at the same time to modify the timeline again, Ride 66 takes place on a single day. This is an important difference from the traditional interpretation of Asia Circuit--because of how the characters' days are set out, Takuto does not have enough time to go to both the shop that Kai was at and to Card Capital. Normally the characters go to school, then go to their shops, then go home. None of the normal attendants of Card Capital such as Shin, Misaki or any of the shop regulars are present when Aichi and Takuto fight, because of how early in the day it is. Takuto fought Aichi after Kai (relative to how Takuto is experiencing time), and it is doubtful that Kai's shop would open earlier than Card Capital.
- Since two modifications were made to the timeline, Asia Circuit is actually in its third timeline, not second as would be typically interpreted. The second timeline is the one where only Kagerou is sealed; in the third timeline, Kagerou, the Royal Paladins and the Shadow Paladins are all sealed.
- Takuto can only modify the timeline relative to the person he is fighting, and only when using Garmore's limit break.
- There are two probable causes of Aichi and Kai's recessive memories from the first timeline; first, both had prolonged contact with PSY Qualia. Second, each individual with recessive memories had their deck modified.
- It is unknown if Takuto retains his memories of the first and second timelines, but if the PSY Qualia theory proves true, he may be immune to his own changes.
- Suiko has not been stated to not remember season 1. As her ability to see Aichi and Ren's visions, as well as sense individuals bearing PSY Qualia suggests that she herself possesses some form of latent Qualia, it is highly probable that she is likewise immune so long as those two are.
- Because the three clans are sealed in the new timeline, the Royal-Shadow civil war never took place. The Gold Paladins are a solidified clan without internal struggles. Because PSY Qualia now hinges on the breaking of the seals rather than on the outcome of the civil war, there is no need for Earth to be synchronized with Cray until the Asia Circuit; as a result of this, the synchronization of Cray and Earth never took place, and Aichi and Ren's PSY Qualia never became dormant. This idea, while not the centerpiece of the alternate timeline theory, is certainly an important point because it means that Aichi is unknowingly still host to his "other self" and Suiko is likely planning a second (or from the third timelines' perspective, first) synchronization.