This character is a Other Letter and is mainly used in the Katakana script.
The glyph is a canonical composition of the glyphs Glyph for U+30A6Katakana Letter U, Glyph for U+3099Combining Katakana-Hiragana Voiced Sound Mark. Its East Asian Width is wide. In bidirectional text it is written from left to right. When changing direction it is not mirrored. This katakana joins with other adjacent katakana to form a word. U+30F4 offers a line break opportunity at its position, except in some numeric contexts.
The Wikipedia has the following information about this codepoint:
U (hiragana: う, katakana: ウ) is one of the Japanese kana, each of which represents one mora. In the modern Japanese system of alphabetical order, they occupy the third place in the modern Gojūon (五十音) system of collating kana. In the Iroha, they occupied the 24th position, between む and ゐ. In the Gojūon chart (ordered by columns, from right to left), う lies in the first column (あ行, "column A") and the third row (う段, "row U"). Both represent the sound [ɯ]. In the Ainu language, the small katakana ゥ represents a diphthong, and is written as w in the Latin alphabet.
The hiragana form with dakuten, ゔ, representing the sound "v", is rarely seen in older words, since the sound does not occur in native Japanese words. However, it is becoming more common with Western influences.