My Sister's Duty妹妹的义务; 동생의 의무

Dongwoo, who happened to found the secret of his squad leader is spending a hellish day because of it. Jungyeon, the younger sister found out about her brother’s suffering through his diary. To protect her brother whom she loves more than anyone else, Jungyeon visits Yoo Jinho, the squad leader… “Oppa… I’ll protect you this time.”