I specialize in setting type for scholarly works requiring CJK characters, where the text is mostly alphabetic with occasional strings of mostly Chinese characters, especially in references. Over the years I’ve written a bunch of GREP queries for InDesign to do things like check strings of chars. lest they begin or end with a letter or digit — in other words, to add an ASCII space — or to pull spaces from within a C or J string. My basic building block is to GREP search for codes, usually with [\x{2E80}-\x{9FBB}]+. That doesn’t get everything, but I know what it misses and I’m less sure of what the might be missed using InDesign’s metacharacter for searching Kanji, ~K (tilde CapK). There are some very useful tidbits in a piece David Blattner posted ten years ago https://indesignsecrets.com/search-for-foreign-language-characters-in-text.php, with the ~K mentioned in the comments.
If your “nothing around the title” holds true, you could GREP search for [\x{2E80}-\x{9FBB}]+ (or perhaps ~K+) and replace with \x{300A}$0\x{300B} (where 300A and 300B are the Unicode values for double Chinese guillemets — substitute as necessary), with the additions picking up the font characteristics of the Chinese string. For most Chinese fonts, each guillemet adds half-a-character-width of whitespace on the outer side. That is often excessive where the string starts, and can look even worse at the end if the closing guillemet is followed by punctuation or a footnote number left dangling. The Japanese fonts bundled with InDesign automatically collapse this extra space, which is fine for Japanese text but can look odd elsewhere. Adobe’s open-source Source Han fonts (Google calls their versions Noto) can also narrow the extra space (these have smarts about the assigned language/locale, but I have not checked whether this affects spacing around guillemets). Also, the guillemets look very different for Adobe Ming (i.e., traditional chars.) and Adobe Song (simplified): many of my jobs use both fonts, but I prefer Adobe Ming’s guillemets, and make them all consistent — and have a char. style on hand with negative tracking to collapse the extra space; on the other hand, Adobe Ming’s double-width period, comma, etc. recall early days, when one form had to work both vertically and horizontally, so now I generally swap in Adobe Song. All of which is a long way of say Chinese punctuation ain’t simple.
Good luck!
David
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