Mr Fuji

former scientist who worked for a Rocket-funded project that eventually gave birth to Leaf's Mewtwo

after a certain incident, he left the scientific community and retired, working at the Lavender Volunteer Pokemon House, looking after abandoned and orphaned pokemon.

at some point Blue tracks him down and kinda guilts him into being Leaf's (and later, any other CHAP's member who makes their way to Lavender Town) physician. He also is more than happy to teach anyone who wants to get into pokemon and human (and pokephiliac) medicine. he sees it as the bare basics of penance he can do to make up for what he's done to help team rocket, even unknowingly