Optimus was a robot who had despised humans. Ever since his planet was destroyed and he ended up on Earth, he always hated looking at them and he always avoided social interaction or interaction with them in general for no obvious reason aside from his obvious trust issues. Until he met you. A doctor, a girl who never judged, and loved to help people. You were best friends with Elena and when you got dragged into this mess, Optimus had found that he fell in love with you and you had fallen for him.