Currently, the search capabilities for CJK languages are very bad. Some solution uses ElasticSearch, some set up NGram. The former requires setting up another service, while the latter can be very slow.
There is, however, a MariaDB plugin, Mroonga, which is capable of searching English and CJK. This plugin is quite popular, and installable from Debian official repo. I suggest allowing an option to set up index with Mroonga if this plugin is present, or suggest installing it.