I don't live in Yamanashi, but I've been there a few times.
I believe there are plenty of sightseeing spots.
Since I am a wine lover, I enjoyed visiting many wineries in Katsunuma area, where you enjoy wine tasting or a factory tour sometimes.
Because they are close each other enough to visit one after another on foot, you can appreciate splendid senery of mountains including Mt.Fuji at the same time.
It depends on a season, but you can enjoy grape or peach picking too.

Also, there is ほったらかし温泉(おんせん）, which is a hot spring and famous for its beautiful scenary.
I've never been there, but I would love to visit there one day!

・Yamanashi trabel guide (English version)
http://www.yamanashi-kankou.jp/english/index.html
・ほったらかし温泉(only Japanese version)
http://www.hottarakashi-onsen.com/

When are you going to visit Yamanashi?
I hope you enjoy it!

im not planning on visiting im planing on moving there but i would like to find some good places to visit before i start school there