One day, a family comes to find a diary belonging to someone from their dying father's study which describes how the person killed multiple people but they are unable to tell if this is a fictional story or a real account by the person and why this was written. Yoshitaka plays the heroine Misako described in the diary who is destined to kill people so as to be at peace with herself emotionally. However, when she comes to understand what true love is, she tries to fight against her fate and struggles with the resulting internal turmoil.
Yoshitaka commented that her character is someone who many people wouldn't be able to understand or identify with so it was a very difficult role for her as well. However, the experience was something hard to come by so she is eagerly awaiting to see the end product once it's ready.
Sources: Nikkansports / Sanspo / Eiga.com