I guess the only scenario that might be semi plausible is if Hector phoned up pretending to be Byuu's brother or something - the Japanese police would be struggling to get ahold of next of kin if the consulate was closed that evening. Although I think that's still immensely unlikely.
Upfront, I 100% believe the suicide thing is today fake manufactured, as Byuu has already gone to strange lengths to get the thread taken down, between getting a compromised mod to risk getting banned to delete it last year (rest in piss
@CIA Nigger ), to throwing another freakout in 4chans /emugen/ over it as recently as last March.
But to play devils advocate of how someone with no relation to him could know he was dead, it would go like this:
Hector is fluent (or at least functional in Japanese)
Somehow doesn't know the real name and address of Byuu during the suicide attempt, but was able contact with someone that does and gets that information after the fact.
Calls up the police in that local prefecture and explains the situation and asks for a wellness check, police check the apartment and find him dead, and inform him. The idea would be that they informed him because he was the one to report it to them, and they did so as a courtesy, beyond the legal requirements of doing so.
Like, if you reported that one of your employees has been a no-show for 3 days and you can't reach them by phone, so you call the cops for a wellness check at their home address, and they let you know the person is dead. They wouldn't tell you that it was a suicide, but as a concerned person who reported the incident in the first place, there's a chance they'd still give you a bit of a heads up.
Now, all of this is bullshit LARP, and most likely Byuu has realized that being a SWE earning well into the 6 figures is worth more than emulating decades old technology for the purpose of muh bleep bloops, and has decided to kill his online persona in a dramatic fashion, with enough drama shitstorm surrounding it to have enough Twitter Troon retard sycophants to attack anyone who questions if he's actually dead.
Shit, look at how the news broke in /emugen/ before it got raided by twitter troons and kiwis warring with each other. The general overall sentiment was "sucks if this is true, but I doubt it's real", given that the people in the community have been well acquainted with Byuu's previous fake suicides and general lolcow behavior.