japanese characters in IE7 – Permalinks

I can’t seem to find an answer to this.

https://www.blog.homelingua.jp

When you view the site in firefox the permalinks/URLs appear in Japanese characters, but in IE they are encoded
eg: https://www.blog.homelingua.jp/category/%E6%9D%B1%E5%8C%97%E9%96%A2%E6%9D%B1%E5%A4%A7%E9%9C%87%E7%81%BD

if you try to copy and paste a link it is also encoded.

You can see this if you select or hover over the coloured category header bars, and some of the posts which only have japanese slugs.

any suggestions for plugins or fixes would be great as I’m coming up with nothing!