remember how in the game, when roxas first dual wields he is holding two kingdom keys and then he turns them into oblivion and oathkeeper? that was the dumbest thing nomura could've done if he wanted it to be clear that roxas was using ven's keyblade and not xion's "keyblade". like why isn't he holding the kingdom key and ventus' keyblade there? that would have made everything so much more clear for every player.
That's the point though, Nomura did not WANT to be clear YET.
You have to remember that Days was released
before Birth by Sleep and having Roxas pull out Wayward Wind would thus have been already a huge spoiler.
Nomura also was not clear in the Days-Interviews either, as there he only spoke about Xion's disappearance "awakening" the second Keyblade within Roxas, and not that Rox was using Xions:
-- In the end Roxas is able use two keyblades. Is this because he now has Xion's?
Nomura: Well, it isn't that Roxas has physically inherited Xion's keyblade, but more that Xion has awakened it within Roxas. In the KH series there are a lot of complex reasons why someone can use a keyblade, but basically you need a "heart" to be able to wield one. So strictly speaking, they are being influenced by Sora. At the present I can't say more than that, since it would go into whether or not Roxas has a heart. And there is also a part that has to do with Xehanort's memories. This time there were connections to the Kingdom Hearts I secret movie, and the time will come when this will have a clear connection as well. You'll just have to ask me then.
Here as usual Nomura is dancing around the subject because he didn't want to spoil anything regarding BBS. In the second part of the answer I bolded he's actually talking about BBS as "Xehanort's memories" were an early synonym for BBS.
In that light we may have also to keep in mind that BBS was originally the only part of the story Nomura and Square Enix planned in advance (while he was working on KH 2, he already had concepts for BBS), as Days was the result of Nintendo requesting another game for their consoles while Coded was requested by Disney if I remember correctly.
The interview snippet Anagram posted about whereit is made clear that Roxas dual-wields Sora's and Ventus' keyblade and that Xion's demise awakened Ven's Keyblade is from the
BBS Ultimania, thus from an information source after the release of BBS. Beating around the bush like in the Days-interviews was thus no longer needed and the reasoning could be clarified directly, which is where the third bolded part of the above snippet comes in.
In the Days-interview Nomura says that the time will come when this has a clear connection as well, and by the time of the BBS Ultimania that time is there.
With both Days and BBS released, Nomura was most likely expecting players to reach the conclusion that Roxas was wielding both Sora's and Ven's Keyblades by themselves, as this is indeed possible with the games alone as it
is made clear in Days that Xion's Keyblade is a "sham" as by Riku's own words, a mere copy and thus not real just like she is.
Xemnas also confirmed within Days that Xion is
copying the powers of the Keyblade from Sora by siphoning his unchained loose memories through Roxas, who thanks to his close connection to Sora acts as a catalyst, again implying that Xion's Keyblade isn't a real one despite copying its effects and powers.
Then there are also the "Secret Reports" of Days written by several Organisation members, in which both Xemnas and Xigbar drop obscure hints towards "him" and "his" possible relation to Roxas and Sora. One report is even called "Him and Roxas" and is written by Xigbar who refers in it to his time where he was still human (which confirms he's talking about Ven because Sora never met Braig so far).
Ven is only ever referred to as "him" of course yet again to avoid too blatant BBS spoilers.
Add on top of this BBS and its revelations of how Ventus is connected to Sora and his heart coming to rest within him in the finale, and you can put two and two together that if a) Xion's Keyblade is a sham, b) Ventus' heart resides in Sora and c) Roxas looks just like Ven most likely due to the close connection between Ven and Sora, who is Roxas' origin, the second Keyblade is most likely Ven's.
You have to collect all these little things from different sources (there are more within the Secret Reports and dialogue bits, but I don't have the time right now to search for them all) and string them together, but you
can reach the same answer as the interviews give eventually.
The interviews only
underline with more emphasis what can be reasonably deduced by combining things learnt from both Days and BBS.
The statement that Xion
awakened the second Keyblade
within Roxas in the Days interview is already a hint at the fact that Roxas is carrying Ventus' heart, which got more implications in the finale of BBS when young Sora allowed Ven's heart to stay with him AND when BBS showed us that foreign hearts entering a body influences its appearance as shown with Terra-Xehanort.
You need a "heart" to wield a Keyblade at all, so Roxas carrying one from the start was a prerequisite for him to be able to physically wield one. The Keyblade itself of course belongs to Sora and that Roxas was able to call on it (and the Keyblade itself allowing Roxas to keep holding it) was due to Roxas' own connection with Sora's heart and him being Sora's Nobody.
Roxas being Ven's "twin-in-appearance" just give more credence to Ven's heart being somehow involved and providing an explanation for the second Keyblade.
It's just that there were also many people who actually
overinterpreted the whole issue coming to the wrong conclusion that Roxas and Ventus are actually one and the same entity, forgetting that Ven's heart was
inactive most of the time and didn't influence Roxas one bit beyond the appearance.
The BBS Ultimania interview then just spills out word for word what could be only deduced beforehand.
I wonder... just how many questions from the Nomura interviews could be answered using in-game sources only?
This sounds almost like a research assignment from school, except I'm actually interested in the topic.
It can definitely be done with
many (but not all) of the mysteries. However it requires very deep digging and dot-connecting with only hints and implications across
multiple games in many cases.
Solving one mystery alone on that can already yield an essay-like post and would be long-winded, which is why using the interview-"Hammer" as a shortcut is most often easier and brings the point across faster since nowadays many people are
not keen on having to read a long essay with references made to multiple games of the series in order to answer
one mystery.
For example the whole "Nobodies can grow new hearts"-fact that so many who don't bother to look into it decry as "retcon" can be derivated with hints and implications from all games starting with Chain of Memories making the "revelation" in DDD nothing but a confirmation of what was kept ambigious and could nonetheless be already suspected.
For someone who saw the implications and hints earlier, this was not a "surprise" in DDD at all and it can be done without referring to a single interview line, but it requires cross-game attention span (and some memory of both dialogue pieces and visual cues) and possibly one or two references to in-game reports.
This is one of the reasons why I have bookmarks for every game-script of the KH games as those include all dialogue for reference searching.
The thing about the dual-wielding Roxas and which the second Keyblade is above also qualifies, although I already shortened that one as much as I possibly could...<__<
Searching for and collecting all those bits across multiple games requires quite some extra work though, especially since the number of games only continues to increase, so resorting to quote a three-line interview paragraph which spills out the facts is also often used as a "shortcut" to give an answer rather than lay out the whole long road to explain it all with the games alone.
