U+3090 Hiragana Letter Wi

The Wikipedia has the following information about this codepoint:

Wi (hiragana: ゐ, katakana: ヰ) is an obsolete Japanese kana (Japanese phonetic characters, each of which represents one mora), which is normally pronounced [i] in current-day Japanese. The combination of a W-column kana letter with ゐ゙ in hiragana was introduced to represent [vi] in the 19th century and 20th century. It is presumed that 'ゐ' represented [wi] , and that 'ゐ' and 'い' represented distinct pronunciations before merging to [i] sometime between the Kamakura and Taishō periods. Along with the kana for we ('ゑ' in hiragana, 'ヱ' in katakana), this kana was deemed obsolete in Japanese with the orthographic reforms of 1946, to be replaced by 'い/イ' in all contexts. It is now rare in everyday usage; in onomatopoeia and foreign words, the katakana form 'ウィ' (U-[small-i]) is used for the mora /wi/.

However, the kana still sees some modern-day usage as a stylistic variant of 'い/イ'. The spelling of whisky is usually uisukii ("ウイスキー"), but is sometimes written uwisukii ("ウヰスキー") stylistically, such as Nikka Whisky (ニッカウヰスキー, nikka uwisukii). The name of the comedy duo Yoiko is written yowiko ("よゐこ"), 2 characters in the video game series Touhou Project have "ゐ" in their names: Tewi Inaba (因幡　てゐ (Inaba Tewi)) & Tenshi Hinanawi (比那名居　天子 (Hinanawi Tenshi)), and the first opening theme to the Future Diary anime series is titled "空想メソロギヰ" (Kuusou Mesorogiwi). The katakana ヰ is sometimes written with a dakuten, 'ヸ', to represent a /vi/ sound in foreign words; however, most IMEs lack a convenient way to do this. It is far more common for /vi/ to be represented by the combination 'ヴィ'.

Hiragana 'ゐ' is still used in one of the Okinawan orthographies, New Okinawan, for the syllable /wi/ and in digraphs for /kwi, ɡwi/. In the Ryukyu University system, the katakana 'ヰ' is used for /i/, while 'い' is /ʔi/. The katakana 'ヰ' is also used in Ainu for /wi/.