I never heard of it before today so know nothing about it. Wikipedia has an extensive discussion of it, https://en.wikipedia.org/wiki/Shinj%C5%AB.

Is this page false with bad references maybe, or was it just a literary tradition and not happening in the real world?

There is a difference between something happening in the real world and it being a tradition.

Erm?

You should be made aware of the fact that unspeakable horror, Japan is more awesome and actually great and traditional.

Double suicides happen all the time around the world and are extensively documented in literature (Romeo and Juliet being the prototypical example). That doesn't mean it is a "tradition".

Wiki suggests otherwise: https://en.wikipedia.org/wiki/Shinjū

The only instance of tradition on that page says it is contained within plays and literature. This is different than saying that the actual act itself, in real life, was a tradition.

The reasonable thing to do is look up the ja.wiki

Here's one citation (14-15 double suicides a year Taisho era in some fashionable district)

https://hdl.handle.net/20.500.14094/0100275627

I agree that suicide ideation is not exactly prosocial, but I think being tolerant of misinformation is a worse look on HN?