Ryakudatsu Kinbaku no Yakata Kanketsu Hen

Deep nested inside of a forest, there's a western-styled mansion. The young man who recently became its owner, lives there together with a beautiful girl. Even though they aren't bloodrelated, they neatly co-habitate as though they were siblings. However, before long, they have already become infatuated with one another. The young man had been staying true to the will of his deceased father who told him on his deathbed: "Track down the whereabouts of your cousin and live together with him." He does as he is told and invites that cousin to his mansion and they begin living together. However, the resident couple didn't think that this would change their fate so drastically... [Translated from DLSite]