In Buso Renkin, Kazuki, the protagonist, wears a red shirt with three odd symbols placed on the chest area:
They're not Latin characters and appear too simple to be Japanese or from other Oriental languages. What are these symbols? Do they mean anything in the story (or, if not, real life)?
It's said that the symbols stand for '963' and is probably a callout to his wife and novelist Kaoru Kurosaki, who collaborated with the author, Nobuhiro Watsuki, on the story for the manga.
There are many ways to read these numbers in Japanese, some that makes sense are:
His wife's Twitter handle is @kaworu963.
As a side note, one of the ships in the Alchemist fleet also bears this number:
