Age Maniax: Isumi Yon Shimai Saigo no Hi

One day protagonist meets with four sisters, who due to certain events starts living in his house. But he has to go to Europe to follow a story, and they decide to go together with him. They make reservations in an old castle which had reports of a princess' ghost, a legendary wolf, a lake monster and a crashed UFO surrounding it. And this is not even the beginning of the events to unfold around t…