This was created by me at 11:22 p.m., so if something is wrong...well, idk. First challenge.

Before we get into the nitty-gritty, you'll need this: Dexter the Bear
And this as well: Story Progression

Now, to the challenge:

You were an emotionless, apathetic girl. You drifted through your life acting like you were normal (having feelings of happiness, sadness, etc.) in order to avoid being called "freaky" or weird. But that all changed in your 2nd year of high school. when you met them...your senpai (we'll call them your lover, k?)... :lovestruc
For the first time, you felt something. A strong desire..a longing..a yearning..a craving. You wanted this person, as they were the only one to EVER make you truly feel something. But as soon as they entered your life...you saw someone...
This person wanted your lover, but not in the same way YOU did. You could give them more affection than they could ever DREAM of. You weren't going to lose the one thing that makes you feel. You don't care who you have to do, as long as your lover isn't with you, they can't be with anyone, ANYONE. To guarantee your lover can't go with someone else, you'll have to.."eliminate" your competition...

CAS:
Create a young adult. They can be any gender (I used female because most yanderes are female), have any skin color, any hairstyle, hair color, etc.
They must have the evil trait, and so they don't mourn the people they kill- I MEAN ELIMINATE, give them the insane trait. You could also give them the Unstable trait if you have ITF You could give them the klepto trait as well: reasons why will be listed soon.

After you create your Yandere, create a new household. This will contain your lover. He/she can look like whatever (remember, they're YOUR lover). Traits don't matter, but I would recommend the friendly and/or good trait.

Optionally, you can create your lover's sibling. Any gender. Make sure they look like your lover! If your lover has green hair and yellow eyes, make their sibling have green hair, yellow eyes, or both. Give them the Family Oriented trait.

Move your yandere and lover into a house (different houses, of course ), and you can start the actual challenge!

Gameplay:
Now, with your SP (story progression) on, you should see other sims talking to your lover. This is fine. BUT, if you see anyone do something romantic with your lover, these sims are considered "rivals" and MUST be eliminated within 5 days. If they aren't, they will confess their love to your lover. He/she will accept it, and you will be left heartbroken...Game Over!

Once you eliminate your first rival, you may talk to your lover, but only once a day for one sim hour. As you eliminate more rivals, you may increase the amount of time you can talk to your lover. (for example, if you eliminate 3 rivals, you can talk to your lover 3 hours a day)

After you began talking to your lover, your goal is to get together with your lover before your yandere becomes an adult. This means to go steady with him/her.

Now, if you did manage to get together with your lover, you need to get married (assuming you weren't as YA's) and have at least 1 baby. You may have as many children as you wish, but one must get the evil and the insane trait as soon as possible.
*MAKE SURE THAT WHEN YOUR YANDERE IS MARRIED, THEIR LOVER TAKES ON HE YANDERE'S LAST NAME. IF THEY DO NOT, GO TO THE TOWN HALL AND CHANGE THEIR NAMES TO THE YANDERE'S MAIDEN NAME*

While your yandere's child is a child, they should make friends, or at least know other kids. You should mark one of these kids as your yan-child's lover. You can also create a family that contains the heir's lover. Once your yan-child is in high school, they must start the yandere process.

The goal of this challenge is to have an entire legacy (10 generations) of yanderes.

Win and Lose Conditions:
You win once you achieve 10 generations of yanderes.

You lose if:
Your rival isn't eliminated within 5 days. Your lover can't love you if they are in love with someone else.
Your yandere dies. Can't have your lover when you're dead!
Your lover dies. Your yandere will fall into a horrible depression and will commit suicide over the loss of the only thing that made her feel alive.
You get caught murdering someone 4 times or by 4 people. They'll have you reported to the police, and you'll be arrested for your crimes.
You couldn't produce a yan-child. Being with your lover is important, but maintaining the family line is also important.
Your lover witnesses you commit murder. He/she will NEVER love you after this, and you'll end up killing them and yourself.
You didn't go steady with your lover before you became an adult. He/she will become uninterested in you, and your advances will always fail.
Your lover's sibling witnesses you commit murder. They will run as fast a possible to your lover's house and tell him/her all about you, resulting in a game over. That little tattle-tail...

Points!:
+3 every time you talk to your lover :lovestruc
+5 every time you eliminate a rival
+10 if you get married as a YA :lovestruc
+5 if you get married after becoming an adult
+5 for every child you have with your lover
+5 for every item you steal from your lover's house (if you have the kleptomaniac trait)
+5 if you and your rival fight and you win (that'll show them )
+20 if you have your lover's sibling.
-5 for every witness that saw your commit murder
-10 if you and your lover have a negative interaction
-20 if you and your lover get into a fight
-10 if you and a rival fight and you lose
-10 if you and your lover try for a baby but couldn't make it happen

Thanks for reading this! Let me know what you think!

bye bye :D

BTW, this challenged is inspired by Yandere Simulator. Go check it out!

As I read the backstory I imagined the intro to Yandere Simulator (some people have made MMDs) and it was her voice XD This is a very interesting challenge!

I'm glad you find the challenge interesting! I listened to the intro to Yandere Simulator, and that inspired me to write the story like it.