There are 50k US citizens in Japan - none dying for months seems impossible.
More likely that whatever source you're citing is only about some small subset of deaths. Even if it's comprehensive on suicides, those often get classified as accidents/natural causes.
But is it even known that Byuu was a US citizen at time of death?
It stops before July, but the emails and suicide are alleged to occur on the 26th and Sunday the 27th*, which suggests it would be there, even if it took locals time to figure out what happened.
He or the Twitter account supposedly posted the passport to confirm he was a citizen at the time, but that's just what I heard.
* https://archive.md/aMcW4 archive of https://docs.google.com/document/d/12pOhaaFh998B0kyc5Sm4Ihlh...
It lists 14 deaths for 2020, when around 500 would be expected. The note at the top clears up that it's not all deaths of US citizen deaths in Japan, so may not include Near's death depending on how it was classified.
It also only includes 1 suicide in 2020 when around 8 would be expected. The numbers are too small to say for certain, but I'd question whether it's comprehensive even for deaths classified as suicide.
> He or the Twitter account supposedly posted the passport to confirm he was a citizen at the time, but that's just what I heard.
I've searched and all I can find are people complaining that a passport was not posted (as proof of death).