Koroshiya-chan to Shinanai Target Killer and Immortal Target

Synopsis

How do you kill a target that can't die? Even worse, how can you possibly kill said target if they give you food, clothes and a hot shower? Will Koroshiya-chan be able to kill the mafia boss Leonardo Amaretto? On top of that... will she be willing to, even when the old man asks her to do so after receiving the kindness he shows her? (Source: MU, edited)