To expand on the above as the OP did not do so, not only does this troper think that Kaitou Corbeau is Toichi but it is pretty obvious that his assistant is Chikage:
- Kaitou Corbeau came to Japan from Las Vegas, where Chikage was and "found a nice man". Chikage returns home just when Kaitou Corbeau appears in Japan, and by telling Kaito not to place heating pads over his body (something only Kaitou Corbeau observed), it becomes clear that she is working with Kaitou Corbeau.
- Kaitou Corbeau sounds and looks exactly like Toichi. While he may be pulling off the same Master of Disguise trick that Kaito usually does, the fact that Aoyama draws him as Toichi implies a lot when he could have just gone with drawing him with a blank mask or another character entirely.
- Kaitou Corbeau wanted Kaito to retire as Kaitou Kid, hence starting that bet with him. Chikage also said in her letter that she returned because she was getting concerned over Kaito being Kaitou Kid and the danger in continuing. Hence, it seems likely that they were both trying to protect their son and get Kaito to stop the Phantom Thief business. Kaitou Corbeau's appearance is to "take over" from Kaitou Kid, much like how Toichi-as-Kaitou-Kid helped to distract people from Phantom Lady's retirement and disappearance.
- As stated in the Midnight Crow chapters, Kuroba means "black feather" which Kaitou Corbeau uses in his thefts and links back to his name of "Corbeau"/crow. It could perfectly well be Kuroba Toichi.
- Lastly, given how Kuroba Toichi was a world-class magician, this troper thinks there is a high chance he could have gotten free in time during the escape trick that supposedly killed him. It's about time we have a WMG that Toichi is actually alive.
- Counter: Such an act could be pulled off by Chikage, or as a set up by someone to test the identity of the current Kaitou KID, a move that has precedence in Detective Conan with how the Black Org tries to confirm or debunk Akai's death and figure out who's involved—something that could even be considered Foreshadowing if the two organizations are one and the same. The Organization did know KID's civilian identity in the past, and by pretending to be the "original" Kaitou KID, Kaitou Corbeau broke KID's Poker Face in about .2 seconds flat and got him to reveal a lot of incriminating information. Heck, I could even see a middle ground of Corbeau being Chikage for the most part, and this hypothetical Mole (possibly Vermouth?) actually offering to step in and "help" Chikage with her plan, simultaneously getting intelligence for someone else.
- When Pandora opened the box, after releasing all the demons and diseases the last thing left int he box was Hope.
- The Hope Diamond is rather large and has an unusual history attached to it. How much is true is questionable.
- While it appears blue to the naked eye under certain light (i.e. short range Ultraviolet) it glows red and continues to glow even after the light source has been removed.
- A possible problem: the Hope Diamond is a cut portion of what was originally a much larger diamond, the French Blue, which was cut down to smuggle it out of France after the French Revolution (and was itself cut from a larger diamond, the Tavernier Blue). Given the amount of attention and focus each incarnation of the diamond had, and the fact that it had to be professionally examined and cut multiple times in its history—including scanned down to the smallest inclusion by some of the top experts on diamonds in the world in order to confirm its identity as a modern incarnation of the French Blue—the likelihood that it is secretly a natural doublet is very, very unlikely. Plus, the Hope Diamond is infamous for supposedly giving its owner bad luck and an early death, and it only turns red in ultraviolet light, not moonlight, two factors which don't resemble the myths surrounding the Pandora gem very much at all. However, I could see it being Pandora cut out of the gem that covered it; Hope was, after all, the last remaining curse found in the depths of Pandora's Box.
- Akako can't cry, because she'll lose her witch status... But it could also be that the tears of a witch grants immortality. The ten thousand year event is actually a prophecy that something will happen during the Volley Comet's passing that will cause her to cry!
- Akako glows red under the moonlight. Kind of. And she's strongly associated with that colour! Also the moonlight could refer to Kaitou Kid, who she has a crush on and sometimes blushes around...
- Akako is beautiful, but the truly beautiful part about her is her heart, which is 'hidden' away. So it's like a gem hidden within a gem. PANDORA.
We don't know much of what happened during the actual magic show, at least not yet, so we can't come up with a detailed idea of movement. Even what we see in Magic Kaitou 1412 isn't specific - and the visuals aren't canon, having changed drastically in every adaptation of the series. What we do know is that Toichi was likely paranoid, though good at hiding it, and probably not only checked his gear, but also checked his stage crew and assistants for their trustworthiness, putting preventative measures in place if he didn't trust the staff, much like KID is known to do during big magic tricks at risky heists. With this in mind, the circumstances become much harder: unless they could quickly work their way into Toichi's trust, the saboteur would have had to be in for the long haul as, more likely, one of Toichi's assistants (stage crews change from performance venue to performance venue, although some tag along with specific performers, and I figure Toichi probably would favor his own, given the threat to his life). But such a long-haul gambit has draw backs: if Toichi became suspicious, they'd have to start over with someone new, and in the meantime, one of their operatives would be occupied for a very long duration during which they can't do much for the organization. Ideally, then, the organization would favor a quicker solution. Family and friends already possessing Toichi's trust would fit.
Logically, the most suspicious people for this are his apprentices, people whom Toichi personally trained. They are also probably the only people who could get away with showing up to one of his shows in disguise without raising his suspicions - they could easily tell him some story about why the disguise was necessary, and then not only would Toichi be at relative ease due to actually knowing the person, but no one else would be able to correctly identify them after Toichi's death - only Toichi would know that they'd come in disguise. The ideal person they need to get in, kill him, and get out of the performance venue quickly, then, is an already-trusted disguise expert Toichi wouldn't bat an eyelash at even if they showed up in disguise - Vermouth, former apprentice and current assassin-of-a-million-faces, would be that ideal.
With this in mind, here's the theory: Vermouth disguises as someone and shows up to the magic show, perhaps offering her assistance to her former master. No one knows her because she's in disguise - but Toichi does, and she gives him some story to explain why the disguise is necessary, probably that she doesn't want to be stalked by the paparazzi and upstage his show. She is a movie star, after all. Because she is his former apprentice, he feels more comfortable letting her backstage, perhaps even letting her help with the show. She takes the opportunity to sabotage his equipment. She may have even acted as one of his assistants on stage, though depending on what kind of trick he was preforming I doubt this, as this would put her close to the blast radius (all versions of his death, though dramatically different between manga, special, and anime, involve some kind of explosive fire), and the heat might react poorly with her disguise if it messes up her makeup or doesn't burn like flesh. The police come and question everyone, and at first chance, she gets away. Nobody ever finds the missing witness, but it doesn't matter - it may look suspicious (enough to convince Jii and possibly Yusaku that it was murder), but either through evidence tampering, a mole in the police force, or sheer efficiency, no one with any formal investigative power realizes a murder has occured, and the blaze is written off as an accident, a simple malfunction of equipment.
This could have happened whether the Black Organization and Magic Kaitou's own criminal organization are the same or not - after all, assassins can be hired, deals can be made between crime groups, and some crime rings can even be sub-groups or puppet-groups of larger ones. The likelihood of them trying to kill Toichi and not at least seeking advice from the underworld assassin who was also his apprentice and operates in the same general underworld circles as them is incredibly small.
As for Kaitou Corbeau: such an act could be pulled off by Chikage, or as a set up by someone to test the identity of the current Kaitou KID (much like the Black Org does in DC when they want to confirm Akai's death and figure out who's involved—so there is precedent). By pretending to be the "original" Kaitou KID, Kaitou Corbeau did break KID's Poker Face in about .2 seconds flat, and got him to reveal a lot of information. Heck, I could see Corbeau being Chikage for the most part, and Vermouth actually offering to step in and "help" Chikage with her plan, with Chikage not knowing Vermouth's... deeper criminal ties. If Toichi is really dead, Vermouth should clearly be the one of, if not the, top suspect.
- It is rather suspicious that despite Snake (and presumably his allies) knowing the first Kaitou KID's civilian identity, no one has come after Kaito despite ostensibly being desperate to find a way to stop KID.
- Toichi being the boss of DC's organization was jossed by a 2016 postcard. He could theoretically be the boss of MK's organization.
- Considering how sneaky Aoyama is and how much he loves Exact Words, this troper isn't sure whether to trust that. Considering what we've now learned from Detective Conan, Toichi could easly be an identity the Boss, Karasuma Renya, assumed sometime in the 50 years since he presumably faked his death. For a character associated with doves, it's pretty strange for the family's last name to be "Black Feather" and for somebody to set up a crow-themed Kaitou using Toichi's identity. Especially since Aoyama has gone out of his way to only use crow symbolism to foreshadow connections with the Black Org. Why persistently align the Kurobas with the color black and crows, when Kid wears white and is associated with doves? We do know, however, that Karasuma considered the crow a personal symbol; he placed it like a seal on his personal possessions, themed his organization after it, and even went out of his way to get a phone number to the tune of a crow-themed song. Considering his symbol matches his name, it's believable he might do the same with one of the identities he assumed. And we do know that Toichi, for whatever reason, was seeking a source of immortality just like the Organization seems to be. In which case, Aoyama's claim of Toichi not being the boss could be a mere "from a certain perspective" kind of thing, because "Karasuma Renya" is the true identity of the Boss, not "Kuroba Toichi."