A Hundred Mists' Murmurs

Do you know how many steps it takes for a monster to grow up?

First, let her meet someone she loves.

Second, let her meet someone who treats her with kindness.

Third, go through her chuunibyou phase with her, and let her do things she believes are righteous.

Finally, tell her about mortality.

The people who love her will die. The people who are gentle with her will leave. And the righteousness she once believed in will rot away.