1. The aunt and other voice we hear are ghosts/zombies/supernatural beings and are trying to lure the young master Leo outside to eat him. Parents are exorcists, Eva is trying hold the supernaturals off as long as she can.
2. Eva kidnapped Leo because family is neglectful, 6 days is when the parents arrive and she can kill them all to keep Leo to herself (least likely scenario, but worth considering)
3. The apocalypse happened and everyone is radioactive or something. Eva is trying to keep Leo from seeing the rainy wasteland outside.
4. Aunt is trying to kill Leo because he’s the heir and she wants father’s position. The aunt tries to assassin ate them on their way to the villa but Eva escapes with Leo and lock themselves in the villa until the parents arrive and she can tell them what happened. (Most realistic scenario, doesn’t explain magical mud tho)