Preston was the youngest of three, the Harlem siblings were the menece of solstice city when their parents
died.It was just the three of them up until Preston was 9 and eventually survival of the fittest took over and they saw that Preston didn't have what it takes to keep up with them so they abandoned him, completely moved cities or possibly regions without even telling Preston, they left in his sleep leaving a note and a small bag of supplies, in the supplies was one empty pokeball and a few Oran berries. After that life was hard for Preston, living on the streets of solstice town where you can be chased and tormented by ghost type pokemon. Which he was for the longest time. Until Shuppet appeard and started to defend him from weaker ghost types. They both started looking after eachother, Shuppet got Preston food and water and in return Preston would protect shuppet when needed, one time he even faced a Gengar in defence of Shuppet. That's when their friendship fully bloomed.
After about another year of their current engadgement Preston grew more and more worrisom of his siblings Maia and Glen. So he decided to leave Solstice Town and start his own Journy. Making the long jounry up to Estoria city to see if they turned up there. Unknowingly, Shuppet followed Him and made his appearance known as soon as he got into Estoria City. He still has not caught Shuppet offically and he will once he get's the chance. See, he has a record and even though he wa aquitted of all charges all police officers and pokemon centers are always wary around him, usually not offering him a place to stay but just a service to his pokemon.
