Satsuriku no Tenshi

When Rachel wakes up in the basement of an unfamiliar building, she finds herself lost all her memory. As Rachel tries to get clear of the basement, she runs into Zack, a scythe-carrying serial killer wrapped from head to toe in bandages. “Kill me, kill me please…" "I will do it, but only if you help me to get out of this building.” The bizarre promise brings these two together and somehow makes them an irreplaceable partner to each other. Where are they? Why are they trapped? And what is the destiny they have been looking for? The journey of death and lives starts… (Source: Crunchyroll)