Bludgeoning Angel Dokuro-chan

In the future, a junior high student, Kusakabe Sakura, will offend God by inventing immortality so that women will stop aging after they turn twelve. Dokuro-chan is an angel from the future sent to kill him. However, Dokuro-chan thinks that Sakura can be spared, so her idea is to constantly occupy Sakura so that he will never be able to invent the...