About COMBINING KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK
Combining Katakana-hiragana Semi-voiced Sound Mark (U+309A) is a Unicode nonspacing mark from the Hiragana block. It resides on Plane 0 (BMP, Basic Multilingual Plane), has bidirectional class NSM (nonspacing mark), is not mirrored, and has combining class 8 (Kana Voicing). In HTML it can be written as ゚ or ゚.