Spoilers are abound in this post so I will cut it immediately to spare those who haven't read the most recent MK chapters the spoilers \o/
For those who already know or don't mind spoilers,
SUP. Canon pretty much hinted a year ago that Kaito and Toichi weren't the only thieves in the family, buuut the hint was so vague and didn't give any background information on this, so it would have been silly to integrate it into canon when it first came out. BUT NOW WE HAVE THE FULL STORY yaaaay! Which means it is time to integrate it into canon! Which means Styx has to revamp a lot of the headcanon she had already come up with in regards to this subject. orz. Also I am working with manga canon here! That includes early, cracky canon! I LOVE THE ANIME REMAKES DON'T GET ME WRONG, but they do differ from their corresponding manga chapters, and since I have been playing Kaito essentially from the manga for over a year now, I'm just going to stick to it. SO WITH THAT SAID, here is how I plan on handling the new canon integration :V
I'm pretty sure Kaito has told people in the past that his mother works night shifts at the local hospital as a nurse, and that he's currently living with her as an only child. This will all have to be retconned |D; Canonically, Kaito is now living by himself (parental supervision does not exist in DCMK) because his mom is traveling! And probably won't be returning to Japan for a while. So if you had a thread with Kaito in which he talked about his mom, a-assume that he said all of that instead.
NEXT COMES... answers to a few questions that were raised for me when I read the chapter. Mainly, when did Kaito learn about his mom being a thief? How much of a role does Chikage play in Kaito's own thiefy adventures? How much did Chikage know about Toichi's thiefy antics and Pandora? STUFF LIKE THAT. Basically, how much of a GODMODEY PARENTS WHO SWEEPS IN TO SAVE HER SON IN TIMES OF NEED is she?
I think canon supports her not being one, thankfully. Which is important, because the way I see it and have always seen it, Kaito's journey into Kaitou Kid, the choices to pick up his father's mantle, the choice to begin stealing in search for answers and the ultimate mission of finding and destroying Pandora is his thing. It's his character growth and development, and taking that away from him by making it so he's always rescued his more experienced mom kind of takes that development away from him. Kaito pretty much jumps into Kaitou Kid with no idea what he's doing with only Jii (who doesn't know everything) as his guide, and throughout the series he makes mistakes and learns from them and betters himself as a thief and peeeerhaps a person (even though his choices are questionably moral). I think it's important for Kaito's choices to have consequences so he can appreciate the depth of the danger he's throwing himself into, aaand because lol he is a thief, and even he realizes that this is not a Wholly Good thing and that he is the Bad Guy in many situations. And because, at this point in canon, I think he really does appreciate the seriousness of his actions and the danger inherent in his job.
ANYWAY I WENT ON A TANGENT THERE. Going back to the original subject, Chikage never really had much development in-series until recently. She was present in the very first chapter of MK and then neeeever appeared again, and while I know Aoyama probably wasn't even thinking about turning her into a thief back then, I THINK THIS WORKS FOR ME. Basically, Kaito goes through volumes 1 - 4 of the manga (and all the DC cases in between) working essentially by himself with Jii as his stagehand, with no hints of his mom ever hopping in to give him advice. I think because of this, it's fair to say that Chikage didn't tell him she was Phantom Lady for this entire period of time. So since Kaito didn't knoooow his mom was a thief, he had to work to keep his new ~*moonlight career*~ from her while continuing to heist as Kaitou Kid. OF COURSE, Chikage obviously knew that Kaito had figured out the secret and was heisting, SO WHY DIDN'T SHE TELL HER SON?
In the beginning of the series, Jii asks Toichi for forgiveness when he tells Kaito about his job as Kid, which is the "Secret [Toichi] wanted him to keep for his life" (awkward translation but assuming, Toichi wanted Jii to keep the Kaitou Kid secret until his grave, which included not telling his son about his night life). Kaito only finds out because he stumbles into the KAITOU CAVE, which was rigged to open after eight years, whiiiich suggests that the Kurobas would rather Kaito have figured out the family secrets by himself. I actually imagine that there was a lot of anxiety on Chikage's part because of this. After all, Toichi was murdered (which I think she knows about, since Jii does), and if Kaito discovered his dad's night life and took after him, then he would be essentially putting himself in the same line of fire as his father, and he could potentially find himself killed too. This anxiety about the profession, plus both parents' unwillingness to tell their son about Kaitou Kid could easily be reason why Chikage didn't tell Kaito even after he became Kid about her stint as Phantom Lady (maybe Chikage was even trying half-heartedly to keep him away from the profession due to Toichi's murder, idek, since I'm sure she figured her son would discover the secret eventually).
SO Kaito becomes Kaitou Kid and, since he's the kind of guy who doesn't share things like this with others because he feels like he has to handle problems like this himself, he doesn't come to his mom with this discovery, either. Chikage starts traveling while Kaito starts learning the ways of the phantom thief, going through volumes 1 - 4 and the DC cases figuring things out on his own. I imagine Chikage kept in contact with Jii during this time, just to make sure Kaito was okay! I doubt she gave him any advice because how would Kaito learn otherwise? THIS FAMILY SEEMS REALLY BIG ON LETTING THEIR KIDS LEARN THINGS FOR THEMSELVES, which I like, so. TL;DR DURING THIS PERIOD KAITO OPERATED WITHOUT CHIKAGE'S INFLUENCE AND ALL WAS WELL.
As for Pandora, Iiii don't think Chikage knows about it! Jii didn't know about it, or at least didn't seem to when Kaito asked. All he really seemed to know was that Toichi was murdered. And since Jii was Toichi's faithful attendant and Chikage his wife, I think it's fair to say that Toichi didn't tell either of them about the Pandora thing. And when Kaito did eventually discover Pandora, I'm pretty sure he told Jii about it... but I'm not sure he told his mom since his discovery of Pandora happened during the period where he was acting without his mom's influence. Idk if Jii would have relayed the information back to Chikage and this is something I actually have to think about a bit more before I make a headcanon decision on it, so I will come back to it. ALL I KNOW IS THAT Kaito would not have told his mom about Pandora, not even after learning she was Phantom Lady, because finding and destroying Pandora is his mission, his revenge, his way of putting his father to rest, and he really needs to do it without her interference. orz.
Speaking of Phantom Lady, since Kaito is aware that his mom is a thief in the most recent chapter, he obviously figures it out eventually. I actually like to think that it's something Kaito did eventually stumble on himself, and he probably only just figured it out a short time before the recent updates and the Ryoma chapter. He probably confronted Chikage about it (over the phone, since she was traveling), and many arguments were had and he's probably still exasperated at her for keeping it from him, but at least he knows now. I can even picture the ~*fond story*~ she tells him of how she met his father occurring like. Right after their argument about it or something. SO HIM FINDING OUT IS A RECENT THING, and he's probably still trying to work out how he feels about it. Beyond exasperated, of course.
And of course, once Chikage is called out on it, she doesn't have to keep the fact that she knows about Kaito and Kid a secret. AND SINCE SHE IS THE TEASING-TYPE, she clearly picks on her son for it and stuff. There's no way she can't not be concerned about his well-being for doing this, though. Not after Toichi was murdered, so maybe the AIRHEADED TEASING DITZY ACT is just her being silly |D; I also think she's probably pretty darn proud of Kaito at this point too, since he essentially did so much on his own without her guidance. Made mistakes, sure, but showed he had a natural talent for this and didn't need to cling to someone's hand to figure it out on his own. It's only after Kaito confronts her about Phantom Lady that she starts getting teasing about it, and I think her dumping the Ryoma heist on him was part of this (and also maybe it was a test to see how far he son had come, idek).
After that, I don't imagine Chikage really gets too involved in Kaito's heists, especially not if she sees he can take care of himself on them (even if he flails). I imagine she still constantly talks to Jii, still keeps tabs on Kaito just to make sure he's safe, and she probably does pick on him or inform him of secret VIGILANTE WORK a la Ryoma for him to do, but her traveling keeps her busy. I imagine she couldn't get too involved in Kaito's heists anyway, because if Toichi's murderers knew he was Kid, and if they see any Kuroba get too close to the Kid heist scene, then they'd probably swoop in to do some serious damage to the Kuroba family. So her staying away is as much protection as it is a chance for Kaito to continue doing his own thing.
RANDOMLY, I LIKE THINKING THAT CHIKAGE TAUGHT TOICHI SOME OF WHAT HE KNOWS. I'm not sure how plausible this is due to how godmod-ish Toichi is, but. You know. It'd be cute.
TL;DR SUMMARY and a timeline of how Styx sees the events happening:
Toichi's murder --> 8 years pass, Chikage keeps both secrets --> Kaito discovers Kid --> Chikage starts traveling, keeps tabs on Kaito from afar via Jii, doesn't divulge Phantom Lady --> Kaito's discovers Pandora after several months of heisting, starts searching for it --> During Kaito's research he learns about Phantom Lady, suspicions happen --> Confronting Mom about Phantom Lady, suspicions confirmed --> Touto Tower incident occurs --> Ryoma heist occurs --> YOU ARE HERE (X) IN CANON.
WHAT IS THIS GOING TO CHANGE IN ROUTE? Absolutely nothing, minus the stuff that had to be retconned. Kaito's still the same person with the same motivations, and his mom also being a thief isn't going to change that (he'll probably be a bit more prone to get exasperated at her, though).
I think most of this makes sense. I hope most of this makes sense. I HAVE NO IDEA IF ANY OF THIS MAKES SENSE. I'm still working with it, and am open to thoughts/suggestions from other people, especially if something doesn't seem to work with canon. I ALSO WELCOME QUESTIONS, they will honestly probably help me work through this even more so it fits with canon.
That's all folks, and if you read all of that, you are kind of an amazing person :V