Japanese Tax on US Mutual Fund Income

In a separate thread, I recently asked about Japanese tax on capital gains from overseas stock sale, and the replies were helpful.

http://www.japan-guide.com/forum/quereadisplay.html?0+151271

Now, about mutual fund income from overseas....

I also have money in some US mutual funds, and I receive quarterly dividends, as well as year-end capital gains distributions.

Does anyone know for sure how those types of investment income are taxed in Japan? Can they be treated to "separation taxation" at a lower (15% + 5%) tax rate?

The mutual funds are largely invested in stocks, if that makes a difference.

If there is a Japanese tax agency webpage or a publication that specifically talks about income from foreign mutual funds, a link to the right webpage would be a huge help.