In the 90s, there were many kogyaru in Shibuya.
Kogyaru fashion was a huge trend among high school girls at the time.
Katakana spelling is standard for this slang term; usually written in kana.
Kanji-kana mixed form; less common than the katakana spelling.
Hiragana-katakana mixed form; rarely used in practice.
The formation is disputed; leading explanations analyze it as 子, “young person,” plus ギャル, or as a shortening of 高校生ギャル, “high-school gal.”