Sidney "Ghost" Kim was born and raised in Santa Teresa, New Mexico. Her father Joaquin "Myth" De Leon was the president of a local Diablos MC chapter and raised his family with similar values to the club itself. Her mother, Yeona Kim, passed away when she and her sister had just turned 7 years old. The girls were told that she had passed away from an unknown illness very suddenly. In reality, she was a victim of an attack from a local street gang trying to wage war against their father. From a very young age, the girls were taught that loss was inevitable and that life isn't a promise. Due to the loss of their mother, the girls were raised by their father and many of the ol ladies from the club would step in to take care of them when he was away on business or when dangerous situations arised.

When the girls reached the age of 21, Serena suggested that they expand their horizons and travel the country living in different places. They picked up a habit of staying in each place for a few months each and then picking up and moving on. They often did a lot of petty crime in the areas they lived in, hoping to be able to turn a decent amount of profit to elongate their travelling years. During the third year of travelling, they were living in Savannah, Georgia. Serena would often be away at strange hours and was very secretive to Sid about what she was doing. Eventually, she confessed to her that she had gotten in with the local street gang, the Phantoms. To Sid's surprise, she had climbed the ranks in just six months and was invited to go to a bank job with them. Sid begged her sister to say no and not go, but she couldn't be convinced. The bank job ended up going horribly wrong and the police shot and killed Serena. This was a devastating loss that left Sid feeling very lost and depressed. No longer wanting to travel, she stayed in Savannah for four years. During this time, she pulled her typical tricks of pick pocketing people in the streets and shoplifting from local stores. This led to her making connections with a group of low-level drug dealers who typically sold to teenagers looking for a cheap high. This eventually ended up being a problem when Alexander "Reaper" Jones, the leader of the Phantoms, caught wind of how much business Sid was getting.

One night, she was going through her usual routine and just selling to the desperate teenagers in the area. Everything seemed to be normal and she was on track to make a good chunk of money. When she showed up to the last sale, something had changed. Sid could feel that this wasn’t the people she was supposed to be selling to. Instead of some tired high school boy that just wanted to get high and forget about school, it was three adult men. One of them had a knife, while the other two were holding pistols. Sweating, she froze in place and waited for them to make their move.

They basically told her that if she wanted to get out alive, she had to give them all of the money she’d made that night and quit selling altogether. However, that wasn’t enough for Reaper. He wanted somebody with her level of street smarts for himself. Instead of letting her go after she dropped the money, they knocked her out with one of their pistols and took her back to their turf. When she woke up, Reaper explained to her that she was his property now. The only way she could get out of it was in a body bag. This was the consequence for messing around in his area. Becoming one of them.

From there, Sidney turned to her friend Savannah Quinn, who eventually helped smuggle her out of state. Savannah's sister Stella Quinn ended up taking Sidney under her wing and introduced her to Jerry Jones and Larkin Kelly. They travelled from El Paso to the pacific northwest. A lot of time was spent together just learning about one another and trying to figure out where to go next. While in Oregon, she got a reaper tattooed on her arm as a reminder of what she was running from and to not be scared. Eventually, JJ let them all know about his family members who were setting up in Los Santos and they all travelled there as a group.

On 3/21/2023, her second day in the city, she was taken by The Yin and Yang Killers and stabbed three times in her abdomen. She now has a large scar as a result. She has tried many times to figure out more information about them but has so far been unsuccessful.

Her introduction to the group (now known as WCMC) began with her introducing herself by saying "Hello, I'm a ghost that's haunting you all. I got serial killed two days ago." This earned her the nickname "Ghost." Sidney was present for the formation of The Wild Cards MC, voting on the name for the group and the founding members. She began prospecting on the day of their first official church on 4/5/2023. She was patched with a unanimous vote into the club on 4/28/2023. On 5/22/23, Imogen "Stitches" McCoy selected Ghost to be one of her enforcers. Her road name was officially changed to "Sunny" on 6/5/2023.

"Hello, I'm a ghost that's haunting you all. I got serial killed two days ago."