U+3057 Hiragana Letter Si

The Wikipedia has the following information about this codepoint:

し, in hiragana, or シ in katakana, is one of the Japanese kana, which each represent one mora. Both represent the phonemes /si/ although for phonological reasons, the actual pronunciation is [ɕi] (listen). The shapes of these kana have origins in the character 之. The katakana form has become increasingly popular as an emoticon in the Western world due to its resemblance to a smiling face.

This character may be combined with a dakuten, forming じ in hiragana, ジ in katakana, and ji in Hepburn romanization; the pronunciation becomes /zi/ (phonetically [d͡ʑi] or [ʑi] in the middle of words).

The dakuten form of this character is used when transliterating "di" occasionally, as opposed to チ's dakuten form, or a de assigned to a small i; for example, Aladdin is written as アラジン Arajin, and radio is written as ラジオ.

In the Ainu language, シ is used to represent the ʃi sound. It can also be written as a small ㇱ to represent a final s sound, pronounced ɕ.