I'm not sure,but I think it's the house were the Katy moves in. If I got owt wrong soz, its cos i havnt been on harvest moon in ages.

Grant is Katys dad and Samanthas husband, so, the house they live in, he lives in. That house is the tall house in the middle of Dr, Hardys house (where Galen used to live) and Wally, Chris, and Hughs house (they're the athletic people). On the map, it is in the area called village houses.