Ghosts want to be seen and acknowledged. When the ally acknowledges the evil spirit as the real owner of Jeongha's body that makes it stronger. When the evil spirit has an ally and prospect of a normal life in the body it wants the body more whereas Jeongha is getting frustrated about "him" doing things he can't remember that makes him want to hold on less. Who keeps the body is about who wants to hold on to the body more - the evil spirit or Jeongha. When the scale tilts in the ghost's favor it is harder for Sora to kick the evil spirit out.
No, I get that. I was just wondering if there was anything I was missing regarding the classmate character and the ghost Jeongha. For example, real Jeongha seemed to be very put off by him and called him gay slurs/ gay derogatorily. I was wondering if there was an implication that the classmate felt particularly strongly about fake Jeongha because he was dating the ghost or something. Or if the ghost had some other connection to the classmate, like being somebody that he had known. It didn’t seem anything was made explicit so I was curious for other people’s interpretation.

Can anyone explain the situation with/importance of the character that was an ally of the evil spirit? What his relationship to it was? I just re read but am still not sure I know what is being implied.