You would be better using graphics made with GD or ImageMagick to display the Kanji.
You can make quotes etc safe using the htmlentities() functions, which converts < > into > / < and " into "e; stuff like that. Stops nasties being added in.
There is also utf8_encode and utf8_decode that may help too.
My RegEx sucks major ass but I'm pretty sure you need to add \i to make it case insensitive, otherwise your only going to match lowercase letters