Naomi

In the Burned Route and Fish Monster Ending, Naomi is a living human. In the former, she is delusional and living alone at the mansion, believing her mother or (non-existent) brother are still alive. In the latter, she is trying to appease the bloodthirsty Naoki.
In the Mother & Father Ending and Twin's Curse Ending, she is a ghost haunting the Mansion. In the former she is trying to help her malevolent mother, while in the latter she is controlled by the Spirit of the mansion to enact the curse.
In the Shadows Ending, she was turned into the Mummy due to Nami's shadow.
In the Monster Curse Ending, she is a ghost forced to feed Naoki. In the Monster Bloodlines Ending, she is a vampire attempting to perform her father's ceremony.
In the Fireflies Ending, she's a ghost that also transforms into the Fish Monster.
In the Epilogues, she is revealed to be just a normal human.