Was it really a Rosary

Why would Kanako be given a fake rosary as her precious item from her mother? Unless, it's more than just a rosary for praying. What if, it was left to her older sister by her mother first, but her sister couldn't unlock its secrets, so it got passed on to her. Now she's been invited to Fuka Academy to find out the secrets it holds and what her mother didn't tell her.