Review Summary: A scam disguised as an album
Before I properly review Showa, I would like to say that while the album's content is pretty bad, my main reason for rating it so low is because of the context behind it, and the reasons The Gerogerigegege had for releasing it. Therefore, I will primarily focus on that in this review.
Showa opens with a low-quality version of the Japanese national anthem, which plays for around a minute, before cutting to silence for a few seconds. The record then quickly cuts to a recording of a couple making love. For the unaware, the album's title and cover refers to the late Japanese Emperor Showa (more commonly known as Hirohito), with the cover being a picture of the Emperor in his old age. So the primary purpose of Showa was not to entertain, but to shock and offend consumers who bought the record, thinking they were buying an album of patriotic music honouring the Emperor; Japanese culture traditionally puts a lot of emphasis on honour, especially towards those of higher social standing, so you could imagine this causing quite a bit of disdain among deceived buyers.
To add insult to injury, Emperor Hirohito died mere months after Showa was released, leading more people to buy patriotic music, and potentially be tricked into buying this album. And while I will admit that this was meant to be a joke, the problem is that it is not a funny joke; Showa is the album equivalent of your annoying friend who thinks that just saying the n-word by itself makes them a comedic genius.
What annoys me even more about Showa is that it quite literally the scams people who The Gerogerigegege wished would buy this record; and The Gerogerigegege likely made a fair amount of money out of this scam. At least a fair amount for an underground Japanese noise act.
So, not only is the content of Showa already pretty bad by itself, the fact that it deceives, offends, scams, and insults its target audience kicks it down multiple rungs to quite possibly the worst album of all time.