The love story of 6 and 9

Sit children, and let me tell you the tale of a guy who was caught in a predicament.

One day a guy was mowing his lawn. He was about a 6, so let's call him that. 6 was mowing his lawn until a dog came running down the street. 6 chased the dog until he caught him. He turned around and saw that a beautiful girl had been chasing the dog too. She was a 9, so lets call her 9. 9 thanked 6 for getting her dog. 6 asked for her number. His palms sweat while 9 made her decision. Success!

6 and 9 started going on dates. Before they knew it, they were in a relationship.

Fast forward a little bit, and in enters 7. 7 is another girl that 6 meets, and she is a 7, so that's why we will call her 7.

6 and 7 start hanging out. 6 thinks that they are just friends, but 7 is romantically interested. One day, 6 introduces 9 to 7. 7 gets extremely jealous and starts being very passive aggressive to 9.

A couple weeks later, 9 tells 6 that 7 had been sending her death threats over FaceBook. She asked 6 to make her stop, and 6 did send her messages over FB, asking her to stop, but 7 didn't reply.

4 weeks later, 6 hasn't heard from either 9 nor 7 over facebook, and he starts to get worried. He is pacing the floor when suddenly, a knock comes at the door. He opens it and waiting for him is a police officer. Officer holds up a picture of 9 and asks, "Is this your girlfriend?"

"Yes," 6 replies. His palms start to get sweaty, sweaty like they did a month or two ago when he asked for 9's number, but it didn't feel the same.

The officer proceeds to say that 7 had committed suicide in her room an that they found remains of 9 in her stomach during the autopsy.

Why was the 6 afraid of the 7?