Oyako Rankan by Alice Soft jap

The main character works in a mansion of the Kamishiro family,
which is comfortably located deep in the mountains.
Lord’s wife, whom he loves as his mother,
her daughters, like older and younger sisters for him.
The hero has to defend these beautiful girls,
for evil intended to impose their cunning paws on them.
To do this, he has to get closer to them,
breaking some prohibitions, but such is the price of their salvation.
Mom and two beautiful daughters - with whom will the hero become truly close? ..