園崎 詩音

She is the younger twin sister of Sonozaki Mion. Despite her personality being seemingly girly and more refined than Mion's personality, thanks to schooling at St. Lucia, she is actually incredibly shrewd, manipulative, and delinquent, moreso than Mion. She hated St. Lucia, calling it a "factory for manufacturing ladies" and got in trouble with the administration numerous times for various misdemeanors.

Higurashi Wiki

In truth, she is the older sister of the Sonozaki twins and as such her true name is Mion, not Shion. She was sent to St. Lucia's Boarding School, but escaped with the help of Kasai Tatsuyoshi, a man who acts like a bodyguard to the Sonozaki family./