Visa Requirement - At least 2 spread blank visa pages

While indeed this is not something other Japan consulates require, alas there is extremely little you can do. You might want to talk to them and ask politely but they might have their own reason, some machine they use, for example.

Let me note this is a very common requirement for other countries as well. For example, this Tripadvisor thread mentions it for a UK visa. This blog post says

Additionally, several countries require at least two blank pages in order to get a visa. For example, South Africa requires Americans who are staying beyond 90 days to obtain a visa, and the passport’s two blank pages must be adjacent. China will issue a six-month visa to a passport with any two blank pages, but in order to receive a 10-year visa, the pages need to be consecutive.

Making Your Passport Last Longer When Running Short Of Pages recommends Post It notes to save double blank pages:

However, if you notice your passport is starting to fill up, grab those sticky notes, write a short and polite message, and stick them in your passport.

I’ve been travelling with these in my passport for over a year now to preserve my last remaining ‘double blank’ page, and all the passport officers I’ve encountered have been most obliging.

Some smile, some laugh and some say nothing at all, but whatever their approach, the interaction has always finished with their stamp being placed somewhere other than those valuable blank pages: typically near other stamps to maximise space, which I always appreciate.

Just one tip: don’t physically write on your passport visa pages (even in pencil), because doing so could render your passport defaced and invalid

The image shows a double blank page with one post it notes on each page, the left one says "Please kindly stamp on any other page. Saving space for one visa." and an arrow to the left and an arrow to the right and then the other page has "space for visa" with the same arrows.