This article's content is accurate to the most recent public game version, 0.4.8d.
The Ghost Maid Game Over is an ending which occurs when you lose to Y's Assassin in Watanabe Inn.
Eric(a) wakes up complaining about feeling cold and having neck pains, but this is normal for one who has been killed by decapitation. Unfortunately, their soul was captured by an unidentified figure in a cloak before they could move on, and is now in service to this being as their maid for the rest of the afterlife.
If they had already been a maid before their untimely death, they at least take positively to their new position and are even happy at the prospect of getting a new co-worker. But if not, then only eternal despair awaits them.