Higurashi When They Cry: Eye Opening Arc

Story :  After a year at boarding school, Shion Sonozaki flees the oppressive
institution and secretly returns to her hometown in the mountains,
telling only her twin sister Mion of her arrival. Though the Sonozaki
family has kept the sisters apart to prevent conflict over who would
become the next family head, Mion and Shion have remained close - enough
so that Shion can easily impersonate her identical twin. When Shion
encounters Satoshi Hojo in town, he is completely taken in by her "Mion"
disguise. And Shion is quite taken with him...