Summary: Deciphering a Japanese family tree requires patience and lots of reference materials.
I’ve written before about how difficult it can be to locate a Japanese gravestone.
Similar challenges face any westerner attempting to read a Japanese family tree. When we visited our cousins at Keishoji, a large copy of a family tree was brought out, which both excited and confounded us. Of course all the names were written in kanji, which neither my mother nor I could read.
The only kanji name I could recognize was my family name, Asai (浅井). And just like on gravestones, no Arabic numbers could be seen, since birth and death dates were written in Japanese and used the years of the era rather than the years of the Gregorian calendar.
Fortunately, the matriarch of Keishoji and two of her sisters sat down with us and helped us translate each name and decipher each year. It took a couple of hours, but we completed the work. I imagine no one on either side of the Pacific Ocean had this information prior this point.