Subaru grew up alone and with out parents. When Subaru was 10 she meet a young woman named Tsukasa and soon fell in love with her. Subaru and Tsukasa were together till Subaru was 15 when Tsukasa was kidnapped. Subaru was teliported to Arcanus by the kidnapper.
During the 5 years Tsukasa and Subaru were together Subaru learned she was a summoner as was Tsukasa. Tsukasa trained Subaru till they were seperated.
Subaru has just arrived in the Academy and is not to happy about it because she is missing her girlfriend who was kidnapped when Subaru was sent to the Academy.