Sa is one of the Japanese kana, which each represent one mora. Both represent. The shapes of these kana originate from 左 and 散, respectively.
Like き, the hiragana character may be written with or without linking the lower line to the rest of the... Wikipedia
hiragana origin: 左
katakana origin: 散
Man'yōgana: 左 佐 沙 作 者 柴 紗 草 散
spelling kana: 桜のサ; (Sakura no "sa")
translit. with dakuten: za