Naomi's mother

In the Burned Route, she died and her corpse mummified.
In the Shadows Ending, her ghost possessed the mansion itself.

In the rest of the routes, she is a reanimated mummy:
In the Mother & Father Ending, she is the antagonist driven by wrath against Kouhei's father for betraying her love, attempting to claim Kouhei for herself.
In the Twins' Curse Ending and Monster Fish Ending, she attempts to protect Nami and Kouhei from the curses after them.
In the Monster Curse Ending, she is forced to sate Naoki's hunger.
In the Monster Family Ending, she was always a mummy and helps with her husband's ceremony.
In the Fireflies Ending, she is a spirit that can manifest as a mummy, lusting over and assaulting Kouhei.
In the Epilogues, she is revealed as having simply been disguised as a mummy.