That pink character is because you applied your western font to the last japanese char. You need a second character style for my grep that only applies the tracking, e.g. a value of 200 or alike. All font related fields should remain blank / unmodified.
Besides, adjust all those [A-z] to include all other western characters that you run into, e.g. [A-Za-z0-9] to match your original grep. I was just a little lazy in typing because my grep style editor appears broken - no cursor keys. ([A-Za-z0-9](?=[^A-Za-z0-9]))|([^A-Za-z0-9](?=[A-Za-z0-9]))
Eventually use the following grep - it is still missing on accented western chars but should cover all plain english:
([[:ascii:]](?=[^[:ascii:]]))|([^[:ascii:]](?=[[:ascii:]]))
For that grep the japanese must not include ascii punctation characters.