This is a chart of who the characters on the names on the left are the real people and the names on the right are who's body they're in.

Yusuke------------------------------------------------------Koenma

Keiko--------------------------------------------------------Kurama

Kuwabara----------------------------------------------------Hiei

Hiei-----------------------------------------------------------Keiko

Kurama------------------------------------------------------Botan

Botan--------------------------------------------------------Yusuke

Koenma-------------------------------------------------------Kuwabara