Japanese Kana consists of two syllabaries: Hiragana and Katakana. The Unicode range for Hiragana is 3040-309F, and for Katakana, it's 30A0-30FF. You can use these ranges to match exclusively Japanese Kana characters in a regular expression.

The regex could look like this:
```regex
/^[\u3040-\u309F\u30A0-\u30FF]*$/
```
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence