She received a phone call from an unknown number. The other line was completely static, but the only word she could hear from that call was "Murdered"; After hanging up she was attacked by someone.

She was about to die, but Ashley healed her wounds before the knights came.  She doesn't feel safe living alone at her apartment, so she decided to tag along with the protagonist to solve the murder cases.

Luna is serious, realistic, and funny when she needs to be.