There's not enough information to really know who Jeff is. He could be anyone - a fictional character, a real person the storyteller knows, or even the storyteller themselves.
Killer Jeff was a modern horror urban legend character from the United States. There were also derivative works such as movies and games. According to different versions of the story, Killer Jeff was a serial killer who had lost his mind. He was a villain protagonist who had the urge to kill to satisfy his urge to kill. He had a smile carved on his face with a knife. He would sneak into the target's house at night and order the victim to go to bed. If the victim did not listen to his orders, he would use a knife to kill the target. There were many different versions and stories about the origin and background of Jeff the Killer. In some versions, Jeff was an ordinary teenager who became violent because he was bullied and eventually became a serial killer. In the game, players needed to find skulls in the dark maze while avoiding the killer Jeff. In general, Killer Jeff was a character full of horror elements and was very popular among horror culture lovers.
A sympathetic view of Jeff in a love story? That's a tough one. Jeff is a symbol of horror and bloodshed. In a love story, the author might try to explore his backstory and find some redeeming qualities, but he has caused so much pain and death. His insanity and love for killing seem to be at the core of his character. So, while we can try to understand him through the lens of a love story, it's still challenging to be fully sympathetic.
Well, one common character is a female love interest. She could be a strong - willed person who is initially scared of Jeff but then gradually falls in love with him. There might also be a sidekick - type character for Jeff, someone who has known him for a while and tries to warn the love interest about Jeff's true nature. And in some fanfictions, there could be a detective - like character who is trying to solve the mystery of Jeff's killings while also getting involved in the love story. This character might be suspicious of the relationship between Jeff and the love interest and tries to break them up for the sake of safety.
" Qing Qing Mo Shang Sang " was a novel written by Lu Guanlan. It told the story of Yu Sangxiao and Long Feimo. Yu Sangxiao had a prominent background, but she was not valued by her family. She was accidentally trapped in a marriage by Long Feimo. This marriage seemed loveless, but it was filled with Long Feimo's protection. In the story, Yu Sangxiao experienced a hunt and a struggle, a fall and a rejection. Even if she tried to escape, she could not avoid it. It was not until the secret hidden in the passage of time surfaced that Yu Sangxiao finally understood Long Feimo's deep love. She also realized her own weakness and the possibility of having someone to rely on quietly. Green Mulberry on the Road was a modern romance novel by Lu Guanlan, published in 2007.
" Qing Qing Mo Shang Sang " was a novel written by Lu Guanlan. It told the story between Yu Sangxiao and Long Feimo. Yu Sangxiao had a prominent background, but she was not valued by her family. She was accidentally trapped in a marriage by Long Feimo. Although the marriage seemed to be loveless at the beginning, it was full of Long Feimo's protection. In the story, there was a plot of hunting and escaping, a plot of falling and being rejected. Even if they escaped and dodged, they could not avoid each other's fate in the end. This novel was about the grievances of the rich and powerful, and the plot was full of twists and turns. Lu Guanlan was an excellent novelist. His works were very popular with readers, including good novels such as " A Homage to the Bard." Qing Qing Mo Shang Sang was one of his original works. Every word was full of gems and was fascinating.
A person who could fall in love with Jeff might be a misfit in society. They don't fit into the normal norms and values, so they are attracted to Jeff's outsider status. This person could also be suffering from some form of mental illness that makes them empathize with Jeff's disturbed mind. They might believe that they can bring some light into Jeff's dark world. Maybe they have a fascination with the macabre and see Jeff as the ultimate expression of that. They are willing to overlook his murderous tendencies in the hope of a deep and unique connection.
There could be his victims. They might not recognize him at first when he turns into a girl and he could use this to get closer to them. Another character could be a mysterious figure who either caused the transformation or is trying to help Jeff reverse it.
The kidnapped victim could be the main character. They would be the focus as they struggle against Jeff. For example, it could be a young girl who shows great courage throughout the ordeal.