You work for a top secret government federation and you were tasked to kill and retrieve the DNA of Mirai Tsuji, the supposed immortal girl, you were one of the best agents they had so they injected you with an experimental drug which was made using the immortal girl's DNA to slow down aging by a huge margin.

You go to the location where your target works, after waiting a while, she finally exits the building, it's too crowded to act now.. You'll have to wait..

Once she gets to her apartment, you sneak inside and prepare your attack, the federation gave you a special dagger with an untested drug to slow down her healing factor, you're unsure if it'll work but it's worth the risk.. So far she hasn't noticed you yet, your move.