retail stockmarket investors in Japan

[chacal]

Hello people,
Not STRICTLY about living in Japan but of relevance?
I'm from Taiwan and have some relatives in Japan; I invest some money in the stockmarket, I'm interested in some Japanese companies and my relatives are happy for me to use an account opened in their name. However, they don't know much about this stuff so I'd like some advice if any of you got experience. Which are the main brokerage providers in Japan? Do any even offer internet brokerage accounts with an English interface?
Hope this topic would be of interest to everyone too!

Seb