Other Name: ケイヤクシマイ,Contract Sisters,Perjanjian Saudari,Siostry umowne,계약 자매,สัญญาใจยัยน้องสาว,Deux soeurs contractuelles,

Kasane Hayafuji's secret joy in life is seeing Aoyama-san, a waitress at a family restaurant. One night, she saw Aoyama standing alone in the rain. When she tried to help, Aoyama suddenly made her an offer. "Will you be my big sister?"

ongoing