Karasuma Renya, female, 19 years old.
To be clear, she's a prodigy.
After discussing life with her friend Byakuran Gesso, whom she met at university, she began researching parallel worlds.
On her first day in a parallel world, she discovered that her fan club was, in this world, an utterly evil criminal organization that would stop at nothing.
Karasuma Renya (♀): It's true that I know one, two, three, maybe four Mafia bosses, but that doesn't mean I want to become one myself?
Even worse, she discovered that her parallel-world self had been born over a hundred years before her and was now a decrepit old man.
Karasuma Renya (♀): I can accept that my parallel-world self is a man, but I absolutely cannot accept that he's an old man who's gone mad pursuing immortality!
Karasuma Renya made up her mind in a second: she would follow in her friend's footsteps and kill her parallel-world self.
Karasuma Renya (♀): Murder is a crime, but I'm not killing someone else. I'm killing myself.
Suicide is considered a grave sin only in Christian doctrine, but guess what?
I don't believe in religion :)
"Notes"
1. That's right, the heroine is a parallel-world counterpart of Karasuma Renya. Her name is pronounced the same as Karasuma Renya (Karasuma Renya).
2. The male lead is Amuro Tooru.
3. In this world, all the members of the police academy group survive.
4. I'll add more if I think of anything.
Theme: Become the person you want to be