Re: Yon/Shi and Nana/Shichi
That's true, the "ichi,...,juu" set is the On pronunciation of the numbers, and is derived from Chinese. The "hitotsu,...,too" set is the Kun pronunciation and is originally Japanese.
I'm learning Chinese, but I don't really know any Japanese and I was surprised that shi also means death in Japanese. In Chinese the word for death is "si" same as the number 4, making it an unlucky number. It's easy to find homophones in a tonal language.