Master Assasin is Acting Lazy again today

Do professional killers find it troublesome to kill people?
Yes, how can we eat, drink, have fun and be free?
So she had an idea... to leave her own mark at the scene of a cold case, so that she could complete the killer's KPI.
However, such a perfect plan was shattered by a second-generation detective fan!
Could it be that her days of just taking advantage of others were over??