What's your opinion on Kuroda Hyoue being the disguised Tsutomu Akai?
I think it would make his character even more interesting, but if he isn't I don't know where and who Tsutomu could be.
And if he is did he meet his kids? I think he met Sera but I am not sure.
"Kuroda Hyoue = Akai Tsutomu" Theory (Updated)
This is my current speculation on Kuroda Hyoue's identity, I will keep it updated as we get new developments.
I think that Kuroda Hyoue is indeed Akai Tsutomu's current identity. Kuroda shares many similarities with Akai Tsutomu and especially his son (Akai Shuuichi). They both have similar fashion sense, with a contrasting white-coloured tie to a dark shirt and a brown overlay, and when it comes to Shuuichi, we got visual cues where they not only stood the same way with hands in their pocket, but also demonstrated the same leg sweep technique (File 989 & 1016), which is most likely intended to indicate that they share the same martial arts (Jeet Kune Do) that Akai Tsutomu was revealed to have mastered (File 1099 & SDB 90+).
Kuroda was also especially interested in the Kohji case, to the point of seemingly noticing a dying message-like name in the news (File 980 & 987). This fits with Akai Tsutomu's interest, that started after Haneda Kohji's father (Haneda Yasuharu), who is Tsutomu's friend, requested that he solved his son's murder (File 1037).
Here is how I currently suspect he turned from a seemingly deceased MI6 agent from Britain to a member of the NPA's Public Security in Japan in the last 17 years.
We know from File 1048-1049 that Tsutomu had a confrontation with Vermouth 17 years ago after his investigation on the Kohji case, and that clash lead to him being presumed dead by the BO. We then learned in File 1099 that Wakasa and a "monster" (Rum) was involved in what potentially was that same incident that lead to his presumed death 17 years ago.
As I speculated before, I think that Tsutomu's investigation lead him to finding out that Kohji's dying message revealed "Karasuma" to be the culprit, and that the prime suspect Asaka is innocent. I think that Rum found out about Tsutomu's investigation and baited him to a location using Vermouth, who disguised as "the innocent bodyguard Asaka" and carried Kohji's shogi piece charm as proof to convince him. Before going to the meeting location, Tsutomu warned his family about making enemies with bad people and told them to move to Japan, so that his family's whereabouts aren't discovered (File 972), in case he doesn't survive the planned meeting with "Asaka" (similar to Mary's contingency plan of having Masumi contact MI6 about fake Tsutomu in case Mary didn't make it back in File 1049).
That lead to Tsutomu finger jabbing Rum's left eye (as hinted by Gosho in the OdaxAoyama interview and File 972) and ultimately getting defeated by Rum after letting his guard down around Vermouth (Fake Asaka/Wakasa).
I suspect that Tsutomu's confrontation with them lead to him surviving (like Mary) and changing his identity and appearance (likely through plastic surgery). Afterwards, to pursue the organization further, it makes sense that he would have moved to Japan, where the culprit(s) "Karasuma" originate from, just like the other overseas agents (i.e Hondou Ethan from the CIA). Just like Mary, who got ahold of a fake pass to fly to Japan (revealed by Gosho in SDB 100+), Tsutomu had also gotten ahold of a fake pass with the alias "Kuroda Hyoue".
I think that he then decided to investigate the Karasuma Group/Black Organization, by becoming a public security officer of the Japanese police (in order to extract information easier, as referenced in File 1033).
In order to get a pass into the police academy in Japan (disregarding of his blank background), I suspect that Kuroda/Tsutomu secretly relied on his relationship with the head of the Ōoka Group (who is currently retired) that was revealed in File 1088, similar to how his friend Haneda Yasuharu did in File 1039-1042.
The Ōoka family has been shown and hinted to have great influence and connections with people in high positions, like the Tokyo governor (File 992), making them more than capable of helping Kuroda/Tsutomu join the japanese police.
In other words, the same time as his eldest son started to work towards becoming an FBI agent 17 years ago (File 972), Kuroda started to work towards getting accepted by the National Police Agency (File 913). He then built himself up and became what I think is the backstage administrator of the NPA's security planning division (who recieves all the classified reports of their NOC:s), all within 7 years.
Seven years later (since his disappearance), Kuroda/Tsutomu has made a name for himself within the NPA and has diligently kept his safe distance from his family, but before the status quo with his family could change, an incident took place around 10 years ago, that lead to his 10-year-long coma (File 914). We recently learned that Iori Muga, the current butler of the Ōoka family, was a former coworker of Kuroda within the Public Security, who went with the alias "Sakakibara" while undercover, which was likely before Kuroda's 10-year coma (File 1090).
I think that what lead to Kuroda's burn-scar-causing and right-eye-losing incident 10 years ago was that Iori Muga (who is actually Rum's true appearance) deemed Kuroda as a threatening and formidable enemy to the black organization. He therefore secretly orchestrated the incident that made Kuroda fall into a coma. Kuroda's hair colour changed due to the stress of the incident (his hair was perhaps shaved off for surgery purposes and white hair grew instead) and he didn't wake up until 10 years later (File 914).
I suspect that when Kuroda/Tsutomu woke up from his coma, he suffered actual memory loss to an extent, which is why he was perceived to have become a different person (As Yui mentioned). This concept was already foreshadowed as a possibility through Vermouth's disguise cover story when she faced Mary as Tsutomu (File 1048).
This would also explain why Kuroda immediately reacted to Wakasa Rumi in the news in File 980, while also still acting unaware of her identity as if he is trying to confirm suspicions of her being a criminal tied to the Kohji case in File 987-989, despite potentially having met her 17 years ago as Tsutomu. The amnesia could have made him forget her potential role in his demise 17 years ago, but he still found her familiar enough to the point of investigating her and making the connection between her name and Kohji's dying message.
While he may have forgotten significant things from his life as Tsutomu, his goal to take down the BO and find out who Kohji's killer is hasn't changed. Although the NPA had him move to Nagano to ease back into his work (before he moved to Tokyo MPD as the new superintendent), I think they gave Kuroda permission to still keep his Backstage administrator role active and stay in contact with their NOC ("Bourbon"/Furuya Rei) by Kuroda's request (File 1017).
